Control of Air Pollution From New Motor Vehicles and New Motor Vehicle Engines; Regulations Requiring Onboard Diagnostic Systems on 2010 and Later Heavy-Duty Engines Used in Highway Applications Over 14,000 Pounds; Revisions to Onboard Diagnostic Requirements for Diesel Highway Heavy-Duty Vehicles Under 14,000 Pounds

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

[Federal Register: January 24, 2007 (Volume 72, Number 15)]
[Proposed Rules]
[Page 3199-3248]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24ja07-30]
[[Page 3200]]

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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 86
[OAR-2005-0047; FRL-8256-9]
RIN 2060-AL92

Control of Air Pollution From New Motor Vehicles and New Motor
Vehicle Engines; Regulations Requiring Onboard Diagnostic Systems on
2010 and Later Heavy-Duty Engines Used in Highway Applications Over
14,000 Pounds; Revisions to Onboard Diagnostic Requirements for Diesel
Highway Heavy-Duty Vehicles Under 14,000 Pounds

AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of proposed rulemaking.

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SUMMARY: In 2001, EPA finalized a new, major program for highway heavy-
duty engines. That program, the Clean Diesel Trucks and Buses program,
will result in the introduction of advanced emissions control systems
such as catalyzed diesel particulate filters (DPF) and catalysts
capable of reducing harmful nitrogen oxide (NO_X) emissions.
This proposal would require that these advanced emissions control
systems be monitored for malfunctions via an onboard diagnostic system
(OBD), similar to those systems that have been required on passenger
cars since the mid-1990s. This proposal would require manufacturers to
install OBD systems that monitor the functioning of emission control
components and alert the vehicle operator to any detected need for
emission related repair. This proposal would also require that
manufacturers make available to the service and repair industry
information necessary to perform repair and maintenance service on OBD
systems and other emission related engine components. Lastly, this
proposal would revise certain existing OBD requirements for diesel
engines used in heavy-duty vehicles under 14,000 pounds.

DATES: If we do not receive a request for a public hearing, written
comments are due March 26, 2007. Requests for a public hearing must be
received by February 8, 2007. If we do receive a request for a public
hearing, we will publish a notice in the Federal Register and on the
Web at http://www.epa.gov/obd/regtech/heavy.htm containing details
regarding the location, date, and time of the public hearing. In that
case, the public comment period would close 30 days after the public
hearing. Under the Paperwork Reduction Act, comments on the information
collection provisions must be received by OMB on or before February 23,
2007.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2005-0047, by one of the following methods:
? http://www.regulations.gov: Follow the on-line
instructions for submitting comments.
? Mail: Onboard Diagnostic (OBD) Systems on 2010 and Later
Heavy-Duty Highway Vehicles and Engines, Environmental Protection
Agency, Mailcode: 6102T, 1200 Pennsylvania Ave., NW., Washington, DC,
20460, Attention Docket ID No. EPA-HQ-OAR-2005-0047. In addition,
please mail a copy of your comments on the information collection
provisions to the Office of Information and Regulatory Affairs, Office
of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th
St. NW., Washington, DC 20503.
Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2005-0047. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected through http://www.regulations.gov
or e-mail. The http://www.regulations.gov Web site
is an ``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov your e-mail address will be
automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses.
Docket: All documents in the docket are listed in the
http://www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the Air Docket, EPA/
DC, EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC.
The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday
through Friday, excluding legal holidays. The telephone number for the
Public Reading Room is (202) 566-1744, and the telephone number for the
Air Docket is (202) 566-1742.

Note: The EPA Docket Center suffered damage due to flooding
during the last week of June 2006. The Docket Center is continuing
to operate. However, during the cleanup, there will be temporary
changes to Docket Center telephone numbers, addresses, and hours of
operation for people who wish to make hand deliveries or visit the
Public Reading Room to view documents. Consult EPA's Federal
Register notice at 71 FR 38147 (July 5, 2006) or the EPA Web site at
http://www.epa.gov/epahome/dockets.htm for current information on
docket operations, locations and telephone numbers. The Docket
Center's mailing address for U.S. mail and the procedure for
submitting comments to http://www.regulations.gov are not affected by the
flooding and will remain the same.

FOR FURTHER INFORMATION CONTACT: U.S. EPA, National Vehicle and Fuel
Emissions Laboratory, Assessment and Standards Division, 2000
Traverwood Drive, Ann Arbor, MI 48105; telephone (734) 214-4405, fax
(734) 214-4816, email sherwood.todd@epa.gov.

SUPPLEMENTARY INFORMATION:

Regulated Entities

This action will affect you if you produce or import new heavy-duty
engines which are intended for use in highway vehicles such as trucks
and buses, or produce or import such highway vehicles, or convert
heavy-duty vehicles or heavy-duty engines used in highway vehicles to
use alternative fuels.
The following table gives some examples of entities that may have
to follow the regulations. But because these are only examples, you
should carefully examine the regulations in 40 CFR part 86. If you have
questions, call the person listed in the FOR FURTHER INFORMATION
CONTACT section of this preamble:

[[Page 3201]]

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Examples of potentially regulated
Category NAICS Codes\a\ SIC Codes\b\ entities
----------------------------------------------------------------------------------------------------------------
Industry................................... 336111 3711 Motor Vehicle Manufacturers; Engine
336112 and Truck Manufacturers.
336120
Industry................................... 811112 7533 Commercial Importers of Vehicles
811198 7549 and Vehicle Components.
541514 8742
Industry................................... 336111 3592 Alternative fuel vehicle
converters.
336312 3714
422720 5172
454312 5984
811198 7549
541514 8742
541690 8931
----------------------------------------------------------------------------------------------------------------
\a\North American Industry Classification Systems (NAICS).
\b\Standard Industrial Classification (SIC) system code.

What Should I Consider as I Prepare My Comments for EPA?

Submitting CBI. Do not submit this information to EPA through
http://www.regulations.gov or e-mail. Clearly mark the part or all of the
information that you claim to be CBI. For CBI information in a disk or
CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as
CBI and then identify electronically within the disk or CD ROM the
specific information that is claimed as CBI). In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2.
Tips for Preparing Your Comments. When submitting comments, remember to:
? Identify the rulemaking by docket number and other
identifying information (subject heading, Federal Register date and
page number).
? Follow directions--The agency may ask you to respond to
specific questions or organize comments by referencing a Code of
Federal Regulations (CFR) part or section number.
? Explain why you agree or disagree; suggest alternatives
and substitute language for your requested changes.
? Describe any assumptions and provide any technical
information and/or data that you used.
? If you estimate potential costs or burdens, explain how
you arrived at your estimate in sufficient detail to allow for it to be
reproduced.
? Provide specific examples to illustrate your concerns, and
suggest alternatives.
? Explain your views as clearly as possible, avoiding the
use of profanity or personal threats.
? Make sure to submit your comments by the comment period
deadline identified.

Outline of this Preamble

I. Overview
A. Background
B. What Is EPA Proposing?
1. OBD Requirements for Engines Used in Highway Vehicles Over
14,000 Pounds GVWR
2. Requirements That Service Information Be Made Available
3. OBD Requirements for Diesel Heavy-Duty Vehicles and Engines
Used in Vehicles Under 14,000 Pounds
C. Why Is EPA Making This Proposal?
1. Highway Engines and Vehicles Contribute to Serious Air
Pollution Problems
2. Emissions Control of Highway Engines and Vehicles Depends on
Properly Operating Emissions Control Systems
3. Basis for Action Under the Clean Air Act
D. How Has EPA Chosen the Level of the Proposed Emissions Thresholds?
E. World Wide Harmonized OBD (WWH-OBD)
F. Onboard Diagnostics for Diesel Engines Used in Nonroad Land-
Based Equipment
1. What Is the Baseline Nonroad OBD System?
2. What Is The Appropriate Level of OBD Monitoring for Nonroad
Diesel Engines?
3. What Should the OBD Standardization Features Be?
4. What Are the Prospects and/or Desires for International
Harmonization of Nonroad OBD?
II. What Are the Proposed OBD Requirements and When Would They Be
Implemented?
A. General OBD System Requirements
1. The OBD System
2. Malfunction Indicator Light (MIL) and Diagnostic Trouble Codes (DTC)
3. Monitoring Conditions
4. Determining the Proper OBD Malfunction Criteria
B. Monitoring Requirements and Timelines for Diesel-Fueled/
Compression-Ignition Engines
1. Fuel System Monitoring
2. Engine Misfire Monitoring
3. Exhaust Gas Recirculation (EGR) System Monitoring
4. Turbo Boost Control System Monitoring
5. Non-Methane Hydrocarbon (NMHC) Converting Catalyst Monitoring
6. Selective Catalytic Reduction (SCR) and Lean NO_X
Catalyst Monitoring
7. NO_X Adsorber System Monitoring
8. Diesel Particulate Filter (DPF) System Monitoring
9. Exhaust Gas Sensor Monitoring
C. Monitoring Requirements and Timelines for Gasoline/Spark-
Ignition Engines
1. Fuel System Monitoring
2. Engine Misfire Monitoring
3. Exhaust Gas Recirculation (EGR) Monitoring
4. Cold Start Emission Reduction Strategy Monitoring
5. Secondary Air System Monitoring
6. Catalytic Converter Monitoring
7. Evaporative Emission Control System Monitoring
8. Exhaust Gas Sensor Monitoring
D. Monitoring Requirements and Timelines for Other Diesel and
Gasoline Systems
1. Variable Valve Timing and/or Control (VVT) System Monitoring
2. Engine Cooling System Monitoring
3. Crankcase Ventilation System Monitoring
4. Comprehensive Component Monitors
5. Other Emissions Control System Monitoring
6. Exceptions to Monitoring Requirements
E. A Standardized Method To Measure Real World Monitoring Performance
1. Description of Software Counters To Track Real World Performance
2. Proposed Performance Tracking Requirements
F. Standardization Requirements
1. Reference Documents
2. Diagnostic Connector Requirements
3. Communications to a Scan Tool
4. Required Emissions Related Functions
5. In-Use Performance Ratio Tracking Requirements
6. Exceptions to Standardization Requirements
G. Implementation Schedule, In-Use Liability, and In-Use Enforcement
1. Implementation Schedule and In-Use Liability Provisions
2. In-Use Enforcement
H. Proposed Changes to the Existing 8,500 to 14,000 Pound Diesel
OBD Requirements

[[Page 3202]]

1. Selective Catalytic Reduction and Lean NO_X Catalyst Monitoring
2. NO_X Adsorber System Monitoring
3. Diesel Particulate Filter System Monitoring
4. NMHC Converting Catalyst Monitoring
5. Other Monitors
6. CARB OBDII Compliance Option and Deficiencies
I. How Do the Proposed Requirements Compare to California's?
III. Are the Proposed Monitoring Requirements Feasible?
A. Feasibility of the Monitoring Requirements for Diesel/
Compression-Ignition Engines
1. Fuel System Monitoring
2. Engine Misfire Monitoring
3. Exhaust Gas Recirculation (EGR) Monitoring
4. Turbo Boost Control System Monitoring
5. Non-Methane Hydrocarbon (NMHC) Converting Catalyst Monitoring
6. Selective Catalytic Reduction (SCR) and NO_X
Conversion Catalyst Monitoring
7. NO_X Adsorber Monitoring
8. Diesel Particulate Filter (DPF) Monitoring
9. Exhaust Gas Sensor Monitoring
B. Feasibility of the Monitoring Requirements for Gasoline/
Spark-Ignition Engines
1. Fuel System Monitoring
2. Engine Misfire Monitoring
3. Exhaust Gas Recirculation (EGR) Monitoring
4. Cold Start Emission Reduction Strategy Monitoring
5. Secondary Air System Monitoring
6. Catalytic Converter Monitoring
7. Evaporative System Monitoring
8. Exhaust Gas Sensor Monitoring
C. Feasibility of the Monitoring Requirements for Other Diesel
and Gasoline Systems
1. Variable Valve Timing and/or Control (VVT) System Monitoring
2. Engine Cooling System Monitoring
3. Crankcase Ventilation System Monitoring
4. Comprehensive Component Monitoring
IV. What Are the Service Information Availability Requirements?
A. What Is the Important Background Information for the Proposed
Service Information Provisions?
B. How Do the Below 14,000 Pound and Above 14,000 Pounds
Aftermarket Service Industry Compare?
C. What Provisions Are Being Proposed for Service Information
Availability?
1. What Information Is Proposed To Be Made Available by OEMs?
2. What Are the Proposed Requirements for Web-Based Delivery of
the Required Information?
3. What Provisions Are Being Proposed for Service Information
for Third Party Information Providers?
4. What Requirements Are Being Proposed for the Availability of
Training Information?
5. What Requirements Are Being Proposed for Reprogramming of Vehicles?
6. What Requirements Are Being Proposed for the Availability of
Enhanced Information for Scan Tools for Equipment and Tool Companies?
7. What Requirements Are Being Proposed for the Availability of
OEM--Specific Diagnostic Scan Tools and Other Special Tools?
8. Which Reference Materials Are Being Proposed for
Incorporation by Reference?
V. What Are the Emissions Reductions Associated With the Proposed
OBD Requirements?
VI. What Are the Costs Associated With the Proposed OBD Requirements?
A. Variable Costs for Engines Used in Vehicles Over 14,000 Pounds
B. Fixed Costs for Engines Used in Vehicles Over 14,000 Pounds
C. Total Costs for Engines Used in Vehicles Over 14,000 Pounds
D. Costs for Diesel Heavy-Duty Vehicles and Engines Used in
Heavy-Duty Vehicles Under 14,000 Pounds
VII. What are the Updated Annual Costs and Costs per Ton Associated
With the 2007/2010 Heavy-Duty Highway Program?
A. Updated 2007 Heavy-Duty Highway Rule Costs Including OBD
B. Updated 2007 Heavy-Duty Highway Rule Costs Per Ton Including OBD
VIII. What Are the Requirements for Engine Manufacturers?
A. Documentation Requirements
B. Catalyst Aging Procedures
C. Demonstration Testing
1. Selection of Test Engines
2. Required Testing
3. Testing Protocol
4. Evaluation Protocol
5. Confirmatory Testing
D. Deficiencies
E. Production Evaluation Testing
1. Verification of Standardization Requirements
2. Verification of Monitoring Requirements
3. Verification of In-Use Monitoring Performance Ratios
IX. What Are the Issues Concerning Inspection and Maintenance Programs?
A. Current Heavy-Duty I/M Programs
B. Challenges for Heavy-Duty I/M
C. Heavy-Duty OBD and I/M
X. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
B. Paperwork Reduction Act
C. Regulatory Flexibility Act (RFA), as Amended by the Small
Business Regulatory Enforcement Fairness Act of 1996 (SBREFA), 5
U.S.C. 601 et. seq.
D. Unfunded Mandates Reform Act
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
I. National Technology Transfer Advancement Act
XI. Statutory Provisions and Legal Authority

I. Overview

A. Background

Section 202(m) of the CAA, 42 U.S.C. 7521(m), directs EPA to
promulgate regulations requiring 1994 and later model year light-duty
vehicles (LDVs) and light-duty trucks (LDTs) to contain an OBD system
that monitors emission-related components for malfunctions or
deterioration ``which could cause or result in failure of the vehicles
to comply with emission standards established'' for such vehicles.
Section 202(m) also states that, ``The Administrator may, in the
Administrator's discretion, promulgate regulations requiring
manufacturers to install such onboard diagnostic systems on heavy-duty
vehicles and engines.''
On February 19, 1993, we published a final rule requiring
manufacturers of light-duty applications to install such OBD systems on
their vehicles beginning with the 1994 model year (58 FR 9468). The OBD
systems must monitor emission control components for any malfunction or
deterioration that could cause exceedance of certain emission
thresholds. The regulation also required that the driver be notified of
any need for repair via a dashboard light, or malfunction indicator
light (MIL), when the diagnostic system detected a problem. We also
allowed optional compliance with California's second phase OBD
requirements, referred to as OBDII (13 CCR 1968.1), for purposes of
satisfying the EPA OBD requirements. Since publishing the 1993 OBD
final rule, EPA has made several revisions to the OBD requirements,
most of which served to align the EPA OBD requirements with revisions
to the California OBDII requirements (13 CCR 1968.2).
On August 9, 1995, EPA published a final rulemaking that set forth
service information regulations for light-duty vehicles and light-duty
trucks (60 FR 40474). These regulations, in part, required each
Original Equipment Manufacturer (OEM) to do the following: (1) List all
of its emission-related service and repair information on a Web site
called FedWorld (including the cost of each item and where it could be
purchased); (2) either provide enhanced information to equipment and
tool companies or make its OEM-specific diagnostic tool available for
purchase by aftermarket technicians, and (3) make reprogramming
capability available to independent service and repair professionals if
its franchised dealerships had such capability. These requirements are
intended to ensure that aftermarket service and repair facilities

[[Page 3203]]

have access to the same emission-related service information, in the
same or similar manner, as that provided by OEMs to their franchised
dealerships. These service information availability requirements have
been revised since that first final rule in response to changing
technology among other reasons. (68 FR 38428)
In October of 2000, we published a final rule requiring OBD systems
on heavy-duty vehicles and engines up to 14,000 pounds GVWR (65 FR 59896).
In that rule, we expressed our intention of developing OBD
requirements in a future rule for vehicles and engines used in vehicles
over 14,000 pounds. We expressed this same intention in our 2007HD
highway final rule (66 FR 5002) which established new heavy-duty
highway emissions standards for 2007 and later model year engines. In
June of 2003, we published a final rule extending service information
availability requirements to heavy-duty vehicles and engines weighing
up to 14,000 pounds GVWR. We declined extending these requirements to
engines above 14,000 pounds GVWR at least until such engines are
subject to OBD requirements.
On January 18, 2001, EPA established a comprehensive national
control program--the Clean Diesel Truck and Bus program--that regulates
the heavy-duty vehicle and its fuel as a single system. (66 FR 5002) As
part of this program, new emission standards will begin to take effect
in model year 2007 and will apply to heavy-duty highway engines and
vehicles. These standards are based on the use of high-efficiency
catalytic exhaust emission control devices or comparably effective
advanced technologies. Because these devices are damaged by sulfur, the
regulation also requires the level of sulfur in highway diesel fuel be
reduced by 97 percent.\1\
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\1\ Note that the 2007HD highway rule contained new emissions
standards for gasoline engines as well as diesel engines.
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Today's action proposes new OBD requirements for highway engines
used in vehicles greater than 14,000 pounds. Today's action also
proposes new availability requirements for emission-related service
information that will make this information more widely available to
the industry servicing vehicles over 14,000 pounds.
In addition to these proposed requirements and changes, we are
seeking comment on possible future regulations that would require OBD
systems on heavy-duty diesel engines used in nonroad equipment. Diesel
engines used in nonroad equipment are, like highway engines, a major
source of NO_X and particulate matter (PM) emissions, and the
diesel engines used in nonroad equipment are essentially the same as
those used in heavy-duty highway trucks. Further, new regulations
applicable to nonroad diesel engines will result in the introduction of
advanced emissions control systems like those expected for highway
diesel engines. (69 FR 38958) Therefore, having OBD systems and OBD
regulations for nonroad engines seems to be a natural progression from
the proposed requirements for heavy-duty highway engines. We discuss
this issue in greater detail in section I of this preamble with the
goal of soliciting public comment regarding how we should proceed with
respect to nonroad OBD.

B. What Is EPA Proposing?

1. OBD Requirements for Engines Used in Highway Vehicles Over 14,000
Pounds GVWR
We believe that OBD requirements should be extended to include over
14,000 pound heavy-duty vehicles and engines for many reasons. In the
past, heavy-duty diesel engines have relied primarily on in-cylinder
modifications to meet emission standards. For example, emission
standards have been met through changes in fuel timing, piston design,
combustion chamber design, charge air cooling, use of four valves per
cylinder rather than two valves, and piston ring pack design and
location improvements. In contrast, the 2004 and 2007 emission
standards represent a different sort of technological challenge that
are being met with the addition of exhaust gas recirculation (EGR)
systems and the addition of exhaust aftertreatment devices such as
diesel particulate filters (DPF), sometimes called PM traps, and
NO_X catalysts. Such ``add on'' devices can experience
deterioration and malfunction that, unlike the engine design elements
listed earlier, may go unnoticed by the driver. Because deterioration
and malfunction of these devices can go unnoticed by the driver, and
because their primary purpose is emissions control, and because the
level of emission control is on the order of 50 to 99 percent, some
form of diagnosis and malfunction detection is crucial. We believe that
such detection can be effectively achieved by employing a well designed
OBD system.
The same is true for gasoline heavy-duty vehicles and engines.
While emission control is managed with both engine design elements and
aftertreatment devices, the catalytic converter is the primary emission
control feature accounting for over 95 percent of the emission control.
We believe that monitoring the emission control system for proper
operation is critical to ensure that new vehicles and engines certified
to the very low emission standards set in recent years continue to meet
those standards throughout their full useful life.
Further, the industry trend is clearly toward increasing use of
computer and electronic controls for both engine and powertrain
management, and for emission control. In fact, the heavy-duty industry
has already gone a long way, absent any government regulation, to
standardize computer communication protocols.\2\ Computer and
electronic control systems, as opposed to mechanical systems, provide
improvements in many areas including, but not limited to, improved
precision and control, reduced weight, and lower cost. However,
electronic and computer controls also create increased difficulty in
diagnosing and repairing the malfunctions that inevitably occur in any
engine or powertrain system. Today's proposed OBD requirements would
build on the efforts already undertaken by the industry to ensure that
key emissions related components will be monitored in future heavy-duty
vehicles and engines and that the diagnosis and repair of those
components will be as efficient and cost effective as possible.
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\2\ See ``On-Board Diagnostics, A Heavy-Duty Perspective,'' SAE
951947; ``Recommended Practice for a Serial Control and
Communications Vehicle Network,'' SAE J1939 which may be obtained
from Society of Automotive Engineers International, 400 Commonwealth
Dr., Warrendale, PA, 15096-0001; and ``Road Vehicles-Diagnostics on
Controller Area Network (CAN)--Part 4: Requirements for emission-
related systems,'' ISO 15765-4:2001 which may be obtained from the
International Organization for Standardization, Case Postale 56, CH-
1211 Geneva 20, Switzerland.
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Lastly, heavy-duty engines and, in particular, diesel engines tend
to have very long useful lives. With age comes deterioration and a
tendency toward increasing emissions. With the OBD systems proposed
today, we expect that these engines will continue to be properly
maintained and therefore will continue to emit at low emissions levels
even after accumulating hundreds of thousands and even a million miles.
For the reasons laid out above, most manufacturers of vehicles,
trucks, and engines have incorporated some type of OBD system into
their products that are capable of identifying when certain types of
malfunctions occur, and in what systems. In the heavy-duty industry,
those OBD systems traditionally have been geared toward

[[Page 3204]]

detecting malfunctions causing drivability and/or fuel economy related
problems. Without specific requirements for manufacturers to include
OBD mechanisms to detect emission-related problems, those types of
malfunctions that could result in high emissions without a
corresponding adverse drivability or fuel economy impact could go
unnoticed by both the driver and the repair technician. The resulting
increase in emissions and detrimental impact on air quality could be
avoided by incorporating an OBD system capable of detecting emission
control system malfunctions.
2. Requirements That Service Information Be Made Available
We are proposing that makers of engines that go into vehicles over
14,000 pounds make available to any person engaged in repair or service
all information necessary to make use of the OBD systems and for making
emission-related repairs, including any emissions-related information
that is provided by the OEM to franchised dealers. This information
includes, but is not limited to, manuals, technical service bulletins
(TSBs), a general description of the operation of each OBD monitor,
etc. We discuss the proposed requirements further in section IV of this
preamble.
The proposed requirements are similar to those required currently
for all 1996 and newer light-duty vehicles and light-duty trucks and
2005 and newer heavy-duty applications up to 14,000 pounds. While EPA
understands that there may be some differences between aftermarket
service for the under 14,000 pound and over 14,000 pound applications,
we believe that any such differences would not substantially affect the
implementation of such requirements and that, therefore, it is
reasonable to use EPA's existing service information regulations as a
basis for proposing service information requirements for the over
14,000 pound arena. See section IV for a complete discussion of the
service information provisions being proposed for the availability of
over 14,000 pound service information.
Note that information for making emission-related repairs does not
include information used to design and manufacture parts, but it may
include OEM changes to internal calibrations and other indirect
information, as discussed in section IV.
3. OBD Requirements for Diesel Heavy-Duty Vehicles and Engines Used in
Vehicles Under 14,000 Pounds
We are also proposing some changes to the existing diesel OBD
requirements for heavy-duty applications under 14,000 pounds (i.e.,
8,500 to 14,000 pounds). Some of these changes are being proposed for
the 2007 and later model years (i.e., for immediate implementation)
because we believe that some of the requirements that we currently have
in place for 8,500 to 14,000 pound applications cannot be met by
diesels without granting widespread deficiencies to industry. Other
changes are being proposed for the 2010 and later model years since
they represent an increase in the stringency of our current OBD
requirements and, therefore, some leadtime is necessary for
manufacturers to comply. All of the changes being proposed for 8,500 to
14,000 pound diesel applications would result in OBD emissions
thresholds identical, for all practical purposes, to the OBD thresholds
being proposed for over 14,000 pound applications.

C. Why Is EPA Making This Proposal?

1. Highway Engines and Vehicles Contribute to Serious Air Pollution
Problems
The pollution emitted by heavy-duty highway engines contributes
greatly to our nation's continuing air quality problems. Our 2007HD
highway rule was designed to address these serious air quality
problems. These problems include premature mortality, aggravation of
respiratory and cardiovascular disease, aggravation of existing asthma,
acute respiratory symptoms, chronic bronchitis, and decreased lung
function. Numerous studies also link diesel exhaust to increased
incidence of lung cancer. We believe that diesel exhaust is likely to
be carcinogenic to humans by inhalation and that this cancer hazard
exists for occupational and environmental levels of exposure.
Our 2007HD highway rule will regulate the heavy-duty vehicle and
its fuel as a single system. As part of this program, new emission
standards will begin to take effect in model year 2007 and phase-in
through model year 2010, and will apply to heavy-duty highway engines
and vehicles. These standards are based on the use of high-efficiency
catalytic exhaust emission control devices or comparably effective
advanced technologies and a cap on the allowable sulfur content in both
diesel fuel and gasoline.
In the 2007HD highway final rule, we estimated that, by 2007,
heavy-duty trucks and buses would account for about 28 percent of
nitrogen oxides emissions and 20 percent of particulate matter
emissions from mobile sources. In some urban areas, the contribution is
even greater. The 2007HD highway program will reduce particulate matter
and oxides of nitrogen emissions from heavy-duty engines by 90 percent
and 95 percent below current standard levels, respectively. In order to
meet these more stringent standards for diesel engines, the program
calls for a 97 percent reduction in the sulfur content of diesel fuel.
As a result, diesel vehicles will achieve gasoline-like exhaust
emission levels. We have also established more stringent standards for
heavy-duty gasoline vehicles, based in part on the use of the low
sulfur gasoline that will be available when the standards go into effect.
2. Emissions Control of Highway Engines and Vehicles Depends on
Properly Operating Emissions Control Systems
The emissions reductions and resulting health and welfare benefits
of the 2007HD highway program will be dramatic when fully implemented.
By 2030, the program will reduce annual emissions of nitrogen oxides,
nonmethane hydrocarbons, and particulate matter by a projected 2.6
million, 115,000 and 109,000 tons, respectively. However, to realize
those large emission reductions and health benefits, the emission
control systems on heavy-duty highway engines and vehicles must
continue to provide the 90 to 95 percent emission control effectiveness
throughout their operating life. Today's proposed OBD requirements will
help to ensure that emission control systems continue to operate
properly by detecting when those systems malfunction, by then notifying
the driver that a problem exists that requires service and, lastly, by
informing the service technician what the problem is so that it can be
properly repaired.
3. Basis for Action Under the Clean Air Act
Section 202(m) of the CAA, 42 U.S.C. 7521(m), directs EPA to
promulgate regulations requiring 1994 and later model year light-duty
vehicles (LDVs) and light-duty trucks (LDTs) to contain an OBD system
that monitors emission-related components for malfunctions or
deterioration ``which could cause or result in failure of the vehicles
to comply with emission standards established'' for such vehicles. Section

[[Page 3205]]

202(m) also states that, ``The Administrator may, in the
Administrator's discretion, promulgate regulations requiring
manufacturers to install such onboard diagnostic systems on heavy-duty
vehicles and engines.''
Section 202(m)(5) of the CAA states that the Administrator shall
require manufacturers to, ``provide promptly to any person engaged in
the repairing or servicing of motor vehicles or motor vehicle engines *
* * with any and all information needed to make use of the emission
control diagnostics system prescribed under this subsection and such
other information including instructions for making emission related
diagnosis and repairs.''

D. How Has EPA Chosen the Level of the Proposed Emissions Thresholds?

The OBD emissions thresholds that we are proposing are summarized
in Tables II.B-1, II.C-1, II.H-1 and II.H-2. These tables show the
actual threshold levels and how they relate to current emissions
standards. Here, we wish to summarize how we chose those proposed
thresholds. First, it is important to note that OBD is more than
emissions thresholds. In fact, most OBD monitors are not actually tied
to an emissions threshold. Instead, they monitor the performance of a
given component or system and evaluate that performance based on
electrical information (e.g., voltage within proper range) or
temperature information (e.g., temperature within range), etc. Such
monitors often detect malfunctions well before emissions are seriously
compromised. Nonetheless, emissions thresholds are a critical element
to OBD requirements since some components and systems, most notably any
aftertreatment devices, cannot be monitored in simple electrical or
temperature related terms. Instead, their operating characteristics can
be measured and correlated to an emissions impact. This way, when those
operating characteristics are detected, an unacceptable emissions
increase can be inferred and a malfunction can be noted to the driver.
Part of the challenge in establishing OBD requirements is
determining the point--the OBD threshold--at which an unacceptable
emissions increase has occurred that is detectable by the best
available OBD technology. Two factors have gone into our determination
of the emissions thresholds we are proposing: technological
feasibility; and the costs and emissions reductions associated with
repairs initiated as a result of malfunctions found by OBD systems. The
first of these factors is discussed in more detail in section III where
we present our case for the technological feasibility of the
thresholds. In summary, we believe that the thresholds we are proposing
are, while challenging, technologically feasible in the 2010 and later
timeframe. We have carefully considered monitoring system capability,
sensor capability, emissions measurement capability, test-to-test
variability and, perhaps most importantly, the manufacturers'
engineering and test cell resources and have arrived at thresholds we
believe can be met on one engine family per manufacturer in the 2010
model year and on all engine families by the 2013 model year.
We believe that the proposed thresholds strike the proper balance
between environmental protection, OBD and various sensor capabilities,
and avoidance of repairs whose costs could be high compared to their
emission control results. One must keep in mind that increasingly
stringent OBD thresholds (i.e., OBD detection at lower emissions
levels) may lead to more durable emission controls due to a
manufacturer's desire to avoid the negative impression given their
product upon an OBD detection. Such an outcome would result in lower
fleetwide emissions while increasing costs to manufacturers. However,
increasingly stringent OBD thresholds may also lead to more OBD
detections and more OBD induced repairs and, perhaps, many OBD induced
repairs for malfunctions having little impact on emissions. Such an
outcome would result in lower fleetwide emissions while increasing
costs to both manufacturers and truck owners.

E. World Wide Harmonized OBD (WWH-OBD)

Within the United Nations (UN), the World Forum for Harmonization
of Vehicle Regulations (WP.29) administers the 1958 Geneva Agreement
(1958 Agreement) to facilitate the adoption of uniform conditions of
approval and reciprocal recognition of approval for motor vehicle
equipment and parts. As a result, WP.29 has responsibility for vehicle
regulations within Europe and, indirectly, many countries outside of
Europe that have voluntarily adopted the WP.29 regulations. The United
States was never a party to the 1958 Agreement, but EPA has monitored
the WP.29 regulations developed under the 1958 Agreement and we have
benefited from a reciprocal consultative relationship with our European
counterparts. More recently, WP.29 took on the responsibility of
administering the 1998 Global Agreement that established a process to
permit all regions of the world to jointly develop global technical
regulations without required mutual recognition of approvals or
designated compliance and enforcement. The United States is a signatory
of the 1998 Global Agreement (1998 Agreement), and EPA has
responsibility for representing the U.S. with respect to environmental
issues within WP.29 as they pertain to the 1998 Agreement.
During the one-hundred-and-twenty-sixth session of WP.29 of March
2002, the Executive Committee (AC.3) of the 1998 Global Agreement (1998
Agreement) adopted a Programme of Work, which includes the development
of a Global Technical Regulation (GTR) concerning onboard diagnostic
systems for heavy-duty vehicles and engines. An informal working
group--the WWH-OBD working group--was established to develop the GTR.
The working group was instructed that the OBD system should detect
failures from the engine itself, as well as from the exhaust
aftertreatment systems fitted downstream of the engine, and from the
package of information exchanged between the engine electronic control
unit(s) and the rest of vehicle and/or powertrain. The working group
was also instructed to base the OBD requirements on the technologies
expected to be industrially available at the time the GTR would be
enforced, and to take into account both the expected state of
electronics in the years 2005-2008 and the expected newest engine and
aftertreatment technologies.
In November 2003, AC.3 further directed the working group to
structure the GTR in such a manner as to enable its future extension to
other functions of the vehicle. In so doing, AC.3 did not revise the
scope of the task given to the working group (i.e., the scope remained
emissions-related heavy-duty OBD). As a result, the GTR is structured
such that OBD monitoring and communications could be extended to other
systems such as vehicle safety systems. This has been achieved by
dividing the GTR into a set of generic OBD requirements to be followed
by specific OBD requirements concerning any future desired OBD systems.
The generic OBD requirements contain definitions and other OBD
regulatory elements that are meant to be applicable throughout the GTR
and all of its modules, annexes, and appendices. This generic section
is followed by the first specific OBD section--emission-related OBD--
which contains definitions and OBD regulatory elements specific to
emissions-related OBD.
EPA has been active in the WWH-OBD working group for more than three

[[Page 3206]]

years. Because that group has been developing a regulation at the same
time that we have been developing the requirements in this proposal,
our proposed OBD requirements are consistent, for the most part, with
the current efforts of the WWH-OBD group.
The WWH-OBD working group submitted a draft GTR as a formal
document in March of 2006. During the months immediately following, the
WWH-OBD working group has made final revisions to the GTR and will
submit it to WP.29 for consideration. If approved by WP.29 and adopted
as a formal global technical regulation, we would intend to propose any
revisions to our OBD regulations that might be necessary to make them
consistent with WWH-OBD.\3\
---------------------------------------------------------------------------

\3\ Note that, while the WWH-OBD GTR is consistent with many of
the specific requirements we are proposing, it is not currently as
comprehensive as our proposal (e.g., it does not contain the same
level of detail with respect to certification requirements and
enforcement provisions). For that reason, at this time, we do not
believe that the GTR would fully replace what we are proposing today.
---------------------------------------------------------------------------

The latest version of the draft WWH-OBD GTR has been placed in the
docket for this rule.\4\ While it is not yet a final document, we are
nonetheless interested in comments regarding the current version. More
specifically, we are interested in comments regarding any possible
inconsistencies between the requirements of the draft GTR and the
requirements being proposed today. We believe that if such
inconsistencies exist, they are minor. WWH-OBD provides a framework for
nations to establish a heavy-duty OBD program. It has the potential to
result in similar OBD systems, but the WWH-OBD GTR must fit into the
context of any country's existing heavy-duty emissions regulations. For
example, at this time, the draft GTR does not specify emissions
threshold levels, implementation dates, or phase-in schedules. As such,
our proposal today is much more detailed than the draft WWH-OBD GTR,
but we believe there exist no major inconsistencies between the two
regulations.
---------------------------------------------------------------------------

\4\ ``Revised Proposal for New Draft Global Technical Regulation
(gtr): Technical Requirements for On-Board Diagnostic Systems (OBD)
for Road Vehicles;'' ECE/TRANS/WP.29/GRPE/2006/8/Rev.1; March 27,
2006, Docket ID# EPA-HQ-OAR-2005-0047-0004.
---------------------------------------------------------------------------

F. Onboard Diagnostics for Diesel Engines Used in Nonroad Land-Based
Equipment

We are also considering regulations--although we are not making any
proposals today--that would require OBD systems on heavy-duty diesel
engines used in nonroad land-based equipment. The pollution emitted by
diesel nonroad engines contributes greatly to our nation's continuing
air quality problems. Our recent Nonroad Tier 4 rulemaking was designed
to address these serious air quality problems from land-based diesel
engines. (69 FR 38958) Like with diesel highway emissions, these
problems include premature mortality, aggravation of respiratory and
cardiovascular disease, aggravation of existing asthma, acute
respiratory symptoms, chronic bronchitis, and decreased lung function.
And, as noted above, we believe that diesel exhaust is likely to be
carcinogenic to humans by inhalation and that this cancer hazard exists
for occupational and environmental levels of exposure.
In our preamble to the Nonroad Tier 4 final rule, we estimated
that, absent the nonroad Tier 4 standards, by 2020, land based nonroad
diesel engines would account for as much as 70 percent of the diesel
mobile source PM inventory. As part of our nonroad Tier 4 program, new
emission standards will begin to take effect in calendar year 2011 that
are based on the use of high-efficiency catalytic exhaust emission
control devices or comparably effective advanced technologies. As with
our 2007HD highway program, a cap is also included on the allowable
sulfur content in nonroad diesel fuel.
The diesel engines used in nonroad land-based equipment are, in
certain horsepower ranges, often essentially the same as those used in
heavy-duty highway trucks. In other horsepower ranges--e.g., very large
nonroad machines with engines having more than 1,500 horsepower--the
engine is quite different. Such differences can include the addition of
cylinders and turbo chargers among other things. Notably, the new
nonroad Tier 4 regulations will result in the introduction of advanced
emissions control systems on nonroad land-based equipment; those
advanced emissions control systems will be the same type of systems as
those expected for highway diesel engines.
Therefore, having OBD systems and OBD regulations for nonroad
diesel engines seems to be a natural progression from the proposed
requirements for heavy-duty highway engines. Nonetheless, we believe
that there are differences between nonroad equipment and highway
applications, and differences between the nonroad market and the
highway market such that proposing the same OBD requirements for
nonroad as for highway may not be appropriate. Therefore, we are
providing advance notice to the public with the goal of soliciting
public comment regarding how we should proceed with respect to nonroad
OBD. This section presents issues we have identified and solicits
comment. We also welcome comment with respect to other issues we have
not addressed here, such as service information availability.
1. What Is the Baseline Nonroad OBD System?
We know that highway diesel engines already use a sophisticated
level of OBD system. For nonroad diesel engines in the 200 to 600
horsepower range--i.e., the typical range of highway engines--are the
current OBD system identical to their highway counterparts? How would
the proposed highway OBD requirements change this, if at all? Do diesel
engines outside the range typical of highway engines use OBD?
2. What Is the Appropriate Level of OBD Monitoring for Nonroad Diesel
Engines?
The proposed OBD requirements for highway engines are very
comprehensive and would result in virtually every element of the
emissions control system being monitored. Is this appropriate for
nonroad diesel engines? And to what degree should such monitoring be
required? The emissions thresholds proposed for highway engines will
push OBD and sensor technology beyond where it is today because of
their stringency. Is a similar level of stringency appropriate for
nonroad engines? Should emissions thresholds analogous to those
presented in Table II.B-1 of this preamble even be a part of any
potential nonroad OBD requirements or should nonroad OBD rely more
heavily on comprehensive component monitoring as discussed in section
II.D.4 of this preamble? This latter question is particularly
compelling given the incredibly broad range of operating
characteristics for nonroad equipment. Similar to the issue of
emissions thresholds, certain aspects of the proposed highway OBD
requirements carry with them serious concerns given the range of use
for heavy-duty highway trucks (line-haul trucks versus garbage trucks
versus urban delivery trucks, etc.). As discussed in various places in
section II of this preamble, this broad range of uses makes it
difficult for manufacturers to design a single approach that would, for
example, ensure frequent monitoring events on all possible
applications. This difficulty could be even more pronounced in the
nonroad industry given the greater number of possible applications.

[[Page 3207]]

We request comment regarding what any potential nonroad OBD
monitoring requirements should look like. More specifically, we request
comment regarding the inclusion of emissions thresholds versus relying
solely on comprehensive component monitoring. From commenters in favor
of emissions thresholds, we request details regarding the appropriate
level of emissions thresholds including data and strong engineering
analyses for/against the suggested level. We request comment regarding
the comprehensiveness of monitoring (i.e., the entire emissions control
system, aftertreatement devices only, feedback control systems only, etc.).
3. What Should the OBD Standardization Features Be?
Should nonroad OBD include a requirement for a dedicated, OBD-only
malfunction indicator light? Should nonroad OBD require specific
communication protocols for communication of onboard information to
offboard devices and scan tools? What should those protocols be? What
are the needs of the nonroad service industry with respect to
standardization of onboard to offboard communications?
4. What Are the Prospects and/or Desires for International
Harmonization of Nonroad OBD?
Nonroad equipment is perhaps the most international of all mobile
source equipment. Land based nonroad equipment, while not as much so as
marine equipment, tends to be designed, produced, marketed, and sold to
a world market to a greater extent than is highway equipment. Given
that, is there a sense within the nonroad industry that international
harmonization is important? Imperative? Is the proper avenue for
putting into place nonroad OBD regulations the WWH-OBD process
discussed above? If so, is industry prepared to play a role in
developing a nonroad OBD element to the WWH-OBD document? Are other
government representatives prepared to do so?

II. What Are the Proposed OBD Requirements and When Would They Be
Implemented?

The following subsections describe our proposed OBD monitoring
requirements and the timelines for their implementation. The
requirements are indicative of our goal for the program which is a set
of OBD monitors that provide robust diagnosis of the emission control
system. Our intention is to provide industry sufficient time and
experience with satisfying the demands of the proposed OBD program.
While their engines already incorporate OBD systems, those systems are
generally less comprehensive and do not monitor the emission control
system in the ways we are proposing. Additionally, the proposed OBD
requirements represent a new set of technological requirements and a
new set of certification requirements for the industry in addition to
the 2007HD highway program and its challenging emission standards for
PM and NO_X and other pollutants. As a result, we believe the
monitoring requirements and timelines outlined in this section
appropriately weigh the need for OBD monitors on the emission control
system and the need to gain experience with not only those monitors but
also the newly or recently added emission control hardware.
We request comment on all aspects of the requirements laid out in
this section and throughout this preamble. As discussed in Section IX,
we are also interested in comments concerning state run HDOBD-based
inspection and maintenance (I/M) programs, the level of interest in
such programs, and comments concerning the suitability of today's
proposed OBD requirements toward facilitating potential HDOBD I/M
programs in the future.

A. General OBD System Requirements

1. The OBD System
We are proposing that the OBD system be designed to operate for the
actual life of the engine in which it is installed. Further, the OBD
system cannot be programmed or otherwise designed to deactivate based
on age and/or mileage of the vehicle during the actual life of the
engine. This requirement is not intended to alter existing law and
enforcement practice regarding a manufacturer's liability for an engine
beyond its regulatory useful life, except where an engine has been
programmed or otherwise designed so that an OBD system deactivates
based on age and/or mileage of the engine.
We are also proposing that computer coded engine operating
parameters not be changeable without the use of specialized tools and
procedures (e.g. soldered or potted computer components or sealed (or
soldered) computer enclosures). Upon Administrator approval, certain
product lines may be exempted from this requirement if those product
lines can be shown to not need such protections. In making the approval
decision, the Administrator will consider such things as the current
availability of performance chips, performance capability of the
engine, and sales volume.
2. Malfunction Indicator Light (MIL) and Diagnostic Trouble Codes (DTC)
Upon detecting a malfunction within the emission control system,\5\
the OBD system must make some indication to the driver so that the
driver can take action to get the problem repaired. The proposal would
require that a dashboard malfunction indicator light (MIL) be
illuminated to inform the driver that a problem exists that needs
attention. Upon illumination of the MIL, the proposal would require
that a diagnostic trouble code (DTC) be stored in the engine's computer
that identifies the detected malfunction. This DTC would then be read
by a service technician to assist in making the necessary repair.
---------------------------------------------------------------------------

\5\ What constitutes a ``malfunction'' for over 14,000 pound
applications under today's proposal is covered in section II.B for
diesel engines, section II.C for gasoline engines, and section II.D
for all engines.
---------------------------------------------------------------------------

Because the MIL is meant to inform the driver of a detected
malfunction, we are proposing that the MIL be located on the driver's
side instrument panel and be of sufficient illumination and location to
be readily visible under all lighting conditions. We are proposing that
the MIL be amber (yellow) in color when illuminated because yellow is
synonymous with the notion of a ``cautionary warning''; the use of red
for the MIL would be strictly prohibited because red signifies
``danger'' which is not the proper message for malfunctions detected
according to today's proposal. Further, we are proposing that, when
illuminated, the MIL display the International Standards Organization
(ISO) engine symbol because this symbol has become accepted after 10
years of light-duty OBD as a communicator of engine and emissions
system related problems. We are also proposing that there be only one
MIL used to indicate all malfunctions detected by the OBD system on a
single vehicle. We believe this is important to avoid confusion over
multiple lights and, potentially, multiple interpretations of those
lights. Nonetheless, we seek comment on this limitation to one
dedicated MIL to communicate emissions-related malfunctions. We also
seek comment on the requirement that the MIL be amber in color since
some trucks may use liquid crystal display (LCD) panels to display
dashboard information and some such panels are monochromic and unable
to display color.
We are also interested in comments regarding the malfunction
indicator light and the symbol displayed to

[[Page 3208]]

communicate that there is an engine and/or emission-related
malfunction. As noted, we are proposing use of the ISO engine symbol as
shown in Table II.A-1. The U.S. Department of Transportation has
proposed use of an alternative ISO symbol to denote, specifically, an
emission-related malfunction. (68 FR 55217) That symbol is also shown
in Table II.A-1. While we are not proposing that this alternative
symbol be used, comments are solicited regarding whether this
alternative symbol provides a clearer message to the driver.
Generally, a manufacturer would be allowed sufficient time to be
certain that a malfunction truly exists before illuminating the MIL. No
one benefits if the MIL illuminates spuriously when a real malfunction
does not exist. Thus, for most OBD monitoring strategies, manufacturers
would not be required to illuminate the MIL until a malfunction clearly
exists which will be considered to be the case when the same problem
has occurred on two sequential driving cycles.\6\
---------------------------------------------------------------------------

\6\ Generally, a ``driving cycle'' or ``drive cycle'' consists
of engine startup and engine shutoff or consists of four hours of
continuous engine operation.
[GRAPHIC]
[TIFF OMITTED] TP24JA07.000

To keep this clear in the onboard computer, we are proposing that
the OBD system make certain distinctions between the problems it has
detected, and that the system maintain a strict logic for diagnostic
trouble code (DTC) storage/erasure and for MIL illumination/
extinguishment. Whenever the enable criteria for a given monitor are
met, we would expect that monitor to run. For continuous monitors, this
would be during essentially all engine operation.\7\ For non-continuous
monitors, it would be during only a subset of engine operation.\8\ In
general, we are proposing that monitors make a diagnostic decision just
once per drive cycle that contains operation satisfying the enable
criteria for the given monitor.
---------------------------------------------------------------------------

\7\ A ``continuous'' monitor--if used in the context of
monitoring conditions for circuit continuity, lack of circuit
continuity, circuit faults, and out-of-range values--means sampling
at a rate no less than two samples per second. If a computer input
component is sampled less frequently for engine control purposes, the
signal of the component may instead be evaluated each time sampling occurs.
\8\ A ``non-continuous'' monitor being a monitor that runs only
when a limited set of operating conditions occurs.
---------------------------------------------------------------------------

When a problem is first detected, we are proposing that a
``pending'' DTC be stored. If, during the subsequent drive cycle that
contains operation satisfying the enable criteria for the given
monitor, a problem in the components/system is not again detected, the
OBD system would declare that a malfunction does not exist and would,
therefore, erase the pending DTC. However, if, during the subsequent
drive cycle that contains operation satisfying the enable criteria for
the given monitor, a problem in the component/system is again detected,
a malfunction has been confirmed and, hence, a ``confirmed'' or ``MIL-
on'' DTC would be stored.\9\ Section II.F presents the requirements for
standardization of OBD information and communications. Upon storage of
a MIL-on DTC and, depending on the communication protocol used--ISO
15765-4 or SAE J1939--the pending DTC would either remain stored or be
erased, respectively. Today's proposal neither stipulates which
communication protocol nor which pending DTC logic be used. We are
proposing to allow the use of either of the existing protocols as is
discussed in more detail in section II.F. Upon storage of the MIL-on
DTC, the MIL must be illuminated.\10\ Also at this time, a
``permanent'' DTC would be stored (see section II.F.4 for more details
regarding permanent DTCs and our rationale for proposing them).\11\
---------------------------------------------------------------------------

\9\ Different industry standards organizations--the Society of
Automotive Engineers (SAE) and the International Standards
Organization (ISO)--use different terminology to refer to a ``MIL-
on'' DTC. For clarity, we use the term ``MIL-on'' DTC throughout
this preamble to convey the concept and not any requirement that
standard making bodies use the term in their standards.
\10\ Throughout this proposal, we refer to MIL illumination to
mean a steady, continuous illumination during engine operation
unless stated otherwise. This contrasts with the MIL illumination
logic used by many engine manufacturers today by which the MIL would
illuminate upon detection of a malfunction but would remain
illuminated only while the malfunction was actually occurring. Under
this latter logic, an intermittent malfunction or one that occurs
under only limited operating conditions may result in a MIL that
illuminates, extinguishes, illuminates, etc., as operating
conditions change.
\11\ A permanent DTC must be stored in a manner such that
electrical disconnections do not result in their erasure (i.e., they
must be stored in non-volatile random access memory (NVRAM)).
---------------------------------------------------------------------------

We are also proposing that, after three subsequent drive cycles
that contain operation satisfying the enable criteria for the given
monitor without any recurrence of the previously detected malfunction,
the MIL should be extinguished (unless there are other MIL-on DTCs
stored for which the MIL must also be illuminated), the permanent DTC
should be erased, but a ``previous-MIL-on'' DTC should remain
stored.\12\ We are proposing that the previous MIL-on DTC remain stored
for 40 engine warmup cycles after which time, provided the identified
malfunction has not been detected again and the MIL is presently not
illuminated for that malfunction, the previous-MIL-on DTC can be
erased.\13\ However, if an illuminated MIL is not extinguished, or if a
MIL-on DTC is not erased, by the OBD system itself but is instead
erased via scan tool or battery disconnect (which would erase all non-
permanent, volatile memory), the permanent DTC must remain stored. This
way, permanent DTCs can only be erased by the OBD system itself and
cannot be erased through human interaction with the system.
---------------------------------------------------------------------------

\12\ This general ``three trip'' condition for extinguishing the
MIL is true for all but two diesel systems/monitors--the misfire
monitor and the SCR system--and three gasoline systems/monitors--the
fuel system, the misfire monitor, and the evaporative system--which
have further conditions on extinguishing the MIL This is discussed
in more detail in sections II.B and II.C.
\13\ For simplicity, the discussion here refers to ``previous-
MIL-on'' DTCs only. The ISO 15765 standard and the SAE J1939
standard use different terms to refer to the concept of a previous-
MIL-on DTC. Our intent is to present the concept of our proposal in
this preamble and not to specify the terminology used by these
standard making bodies.
---------------------------------------------------------------------------

We are proposing that the manufacturer be allowed, upon

[[Page 3209]]

Administrator approval, to use alternative statistical MIL illumination
and DTC storage protocols to those described above (i.e., alternatives
to the ``first trip--pending DTC, second strip--MIL-on DTC logic). The
Administrator would consider whether the manufacturer provided data
and/or engineering evaluation adequately demonstrates that the
alternative protocols can evaluate system performance and detect
malfunctions in a manner that is equally effective and timely.
Alternative strategies requiring, on average, more than six driving
cycles for MIL illumination would probably not be accepted.
Upon storage of either a pending DTC and/or a MIL-on DTC, we are
proposing that the computer store a set of ``freeze frame'' data. This
freeze frame data would provide a snap shot of engine operating
conditions present at the time the malfunction occurred and was
detected. This information serves the repair technician in diagnosing
the problem and conducting the proper repair. The freeze frame data
should be stored upon storage of a pending DTC. If the pending DTC
matures to a MIL-on DTC, the manufacturer can choose to update the
freeze frame data or retain the freeze frame stored in conjunction with
the pending DTC. Likewise, any freeze frame stored in conjunction with
any pending or MIL-on DTC should be erased upon erasure of the DTC.
Further information concerning the freeze frame requirement and the
data required in the freeze frame is presented in section II.F.4, below.
We are also proposing that the OBD system illuminate the MIL and
store a MIL-on DTC to inform the vehicle operator whenever the engine
enters a mode of operation that can affect the performance of the OBD
system. If such a mode of operation is recoverable (i.e., operation
automatically returns to normal at the beginning of the following
ignition cycle \14\), then in lieu of illuminating the MIL when the
mode of operation is entered, the OBD system may wait to illuminate the
MIL and store the MIL-on DTC if the mode of operation is again entered
before the end of the next ignition cycle. We are proposing this
because many operating strategies are designed such that they continue
automatically through to the next key-off. Regardless, upon the next
key-on, the engine control would start off in ``normal'' operating mode
and would return to the ``abnormal'' operating mode only if the
condition causing the abnormal mode was again encountered. In such
cases, we are proposing to allow that the MIL be illuminated during the
second consecutive drive cycle during which such an ``abnormal'' mode
is engaged.\15\
---------------------------------------------------------------------------

\14\ ``Ignition Cycle'' means a drive cycle that begins with
engine start and includes an engine speed that exceeds 50 to 150
rotations per minute (rpm) below the normal, warmed-up idle speed
(as determined in the drive position for vehicles equipped with an
automatic transmission) for at least two seconds plus or minus one second.
\15\ Note that we use the term ``abnormal'' to refer to an
operating mode that the engine is designed to enter upon determining
that ``normal'' operation cannot be maintained. Therefore, the term
``abnormal'' is somewhat of a misnomer since the engine is doing
what it has been designed to do. Nonetheless, the abnormal operating
mode is clearly not the operating mode the manufacturer has intended
for optimal operation. Such operating modes are sometimes referred
to as ``default'' operating modes or ``limp-home'' operating modes.
---------------------------------------------------------------------------

Whether or not the ``abnormal'' mode of operation is recoverable,
in this context, has nothing to do with whether the detected
malfunction goes away or stays. Instead, it depends solely on whether
or not the engine, by design, will stay in abnormal operating mode on
the next key-on. We are proposing this MIL logic because often the
diagnostic (i.e., monitor) that caused the engine to enter abnormal
mode cannot run again once the engine is in the abnormal mode. So, if
the MIL logic associated with abnormal mode activation was always a
two-trip diagnostic, abnormal mode activation would set a pending DTC
on the first trip and, since the system would then be stuck in that
abnormal operating mode and would never be able to run the diagnostic
again, the pending DTC could never mature to a MIL-on DTC nor
illuminate the MIL. Hence, the MIL must illuminate upon the first entry
into such an abnormal operating mode. If such a mode is recoverable,
the engine will start at the next key-on in ``normal'' mode allowing
the monitor to run again and, assuming another detection of the
condition, the system would set a MIL-on DTC and illuminate the MIL.
The OBD system would not need to store a DTC nor illuminate the MIL
upon abnormal mode operation if other telltale conditions would result
in immediate action by the driver. Such telltale conditions would be,
for example, an overt indication like a red engine shut-down warning
light. The OBD system also need not store a DTC nor illuminate the MIL
upon abnormal mode operation if the mode is indeed an auxiliary
emission control device (AECD) approved by the Administrator.
There may be malfunctions of the MIL itself that would prevent it
from illuminating. A repair technician--or possibly an I/M inspector--
would still be able to determine the status of the MIL (i.e., commanded
``on'' or ``off'') by reading electronic information available through
a scan tool, but there would be no indication to the driver of an
emissions-related malfunction should one occur. Unidentified
malfunctions may cause excess emissions to be emitted from the vehicle
and may even cause subsequent deterioration or failure of other
components or systems without the driver's knowledge. In order to
prevent this, the manufacturer must ensure that the MIL is functioning
properly. For this reason, we are proposing two requirements to check
the functionality of the MIL itself. First, the MIL would be required
to illuminate for a minimum of five seconds when the vehicle is in the
key-on, engine-off position. This allows an interested party to check
the MIL's functionality simply by turning the key to the key-on
position. While the MIL would be physically illuminated during this
functional check, the data stream value for the MIL command status
would be required to indicate ``off'' during this check unless, of
course, the MIL was currently being commanded ``on'' for a detected
malfunction. This functional check of the MIL would not be required
during vehicle operation in the key-on, engine-off position subsequent
to the initial engine cranking of an ignition cycle (e.g., due to an
engine stall or other non-commanded engine shutoff).
The second functional check requirement we are proposing requires
the OBD system to perform a circuit continuity check of the electrical
circuit that is used to illuminate the MIL to verify that the circuit
is not shorted or open (e.g., a burned out bulb). While there would not
be an ability to illuminate the MIL when such a malfunction is
detected, the electronically readable MIL command status in the onboard
computer would be changed from commanded ``off'' to ``on''. This would
allow the truck owner or fleet maintenance staff to quickly determine
whether an extinguished MIL means ``no malfunctions'' or ``broken
MIL.'' It would also serve, should it become of interest in the future,
complete automation of the I/M process by eliminating the need for
inspectors to input manually the results of their visual inspections.
Feedback from passenger car I/M programs indicates that the current
visual bulb check performed by inspectors is subject to error and
results in numerous vehicles being falsely failed or passed. By
requiring monitoring of the circuit itself, the entire pass/fail
criteria of an I/M program could be determined by the electronic
information available through a scan tool, thus better facilitating quick

[[Page 3210]]

and effective inspections and minimizing the chance for manually-
entered errors.
At the manufacturer's option, the MIL may be used to indicate
readiness status in a standardized format (see Section II.F) in the
key-on, engine-off position. Readiness status is a term used in light-
duty OBD that refers to a vehicle's readiness for I/M inspection. For a
subset of monitors--those that are non-continuous monitors for which an
emissions threshold exists (see sections II.B and II.C for more on
emissions thresholds)--a readiness status indicator must be stored in
memory to indicate whether or not that particular monitor has run
enough times to make a diagnostic decision. Until the monitor has run
sufficient times, the readiness status would indicate ``not ready''.
Upon running sufficient times, the readiness status would indicate
``ready.'' This serves to protect against drivers disconnecting their
battery just prior to the I/M inspection so as to erase any MIL-on
DTCs. Such an action would simultaneously set all readiness status
indicators to ``not ready'' resulting in a notice to return to the
inspection site at a future date. Readiness indicators also help repair
technicians because, after completing a repair, they can operate the
vehicle until the readiness status indicates ``ready'' and, provided no
DTCs are stored, know that the repair has been successful. We are
proposing that HDOBD systems follow this same readiness status logic as
used for years in light-duty OBD both to assist repair technicians and
to facilitate potential future HDOBD I/M programs.
We are also proposing that the manufacturer, upon Administrator
approval, be allowed to use the MIL to indicate which, if any, DTCs are
currently stored (e.g., to ``blink'' the stored codes). The
Administrator would approve the request if the manufacturer can
demonstrate that the method used to indicate the DTCs will not be
unintentionally activated during any inspection test or during routine
driver operation.
3. Monitoring Conditions
a. Background
Given that the intent of the proposed OBD requirements is to
monitor the emission control system for proper operation, it is logical
that the OBD monitors be designed such that they monitor the emission
control system during typical driving conditions. While many OBD
monitors would be designed such that they are continuously making
decisions about the operational status of the engine, many--and
arguably the most critical--monitors are not so designed. For example,
an OBD monitor whose function is to monitor the active fuel injection
system of a NO_X adsorber or a DPF cannot be continuously
monitoring that function since that function occurs on an infrequent
basis. This OBD monitor presumably would be expected to ``run,'' or
evaluate the active injection system, during an actual fuel injection event.
For this reason, manufacturers are allowed to determine the most
appropriate times to run their non-continuous OBD monitors. This way,
they are able to make an OBD evaluation either at the operating
condition when an emission control system is active and its operational
status can best be evaluated, and/or at the operating condition when
the most accurate evaluation can be made (e.g., highly transient
conditions or extreme conditions can make evaluation difficult).
Importantly, manufacturers are prohibited from using a monitoring
strategy that is so restrictive such that it rarely or never runs. To
help protect against monitors that rarely run, we are proposing an
``in-use monitor performance ratio'' requirement which is detailed in
section II.E.
The set of operating conditions that must be met so that an OBD
monitor can run are called the ``enable criteria'' for that given
monitor. These enable criteria are often different for different
monitors and may well be different for different types of engines. A
large diesel engine intended for use in a Class 8 truck would be
expected to see long periods of relatively steady-state operation while
a smaller engine intended for use in an urban delivery truck would be
expected to see a lot of transient operation. Manufacturers will need
to balance between a rather loose set of enable criteria for their
engines and vehicles given the very broad range of operation HD highway
engines see and a tight set of enable criteria given the desire for
greater monitor accuracy.
b. General Monitoring Conditions
i. Monitoring Conditions for All Engines
As guidance to manufacturers, we are proposing the following
criteria to assist manufacturers in developing their OBD enable
criteria. These criteria would be used by the Agency during our OBD
certification approval process to ensure that monitors run on a frequent
basis during real world driving conditions. These criteria would be:
? The monitors should run during conditions that are
technically necessary to ensure robust detection of malfunctions (e.g.,
to avoid false passes and false indications of malfunctions);
? The monitor enable criteria should ensure monitoring will
occur during normal vehicle operation; and,
? Monitoring should occur during at least one test used by
EPA for emissions verification `` either the HD Federal Test Procedure
(FTP) transient cycle, or the Supplementary Emissions Test (SET).\16\
---------------------------------------------------------------------------

\16\ See 40 CFR part 86, subpart N for details of EPA's test procedures.
---------------------------------------------------------------------------

As discussed in more detail in sections II.B through II.D, we are
proposing that manufacturers define the monitoring conditions, subject
to Administrator approval, for detecting the malfunctions required by
this proposal. The Administrator would determine if the monitoring
conditions proposed by the manufacturer for each monitor abide by the
above criteria.
In general, except as noted in sections II.B through II.D, the
proposed regulation would require each monitor to run at least once per
driving cycle in which the applicable monitoring conditions are met.
The proposal would also require certain monitors to run continuously
throughout the driving cycle. These include a few threshold monitors
(e.g., fuel system monitor) and most circuit continuity monitors. While
a basic definition of a driving cycle (e.g., from ignition key-on and
engine startup to engine shutoff) has been sufficient for passenger
cars, the driving habits of many types of vehicles in the heavy-duty
industry dictate an alternate definition. Specifically, many heavy-duty
operators will start the engine and leave it running for an entire day
or, in some cases, even longer. As such, we are proposing that any
period of continuous engine-on operation of four hours be considered a
complete driving cycle. A new driving cycle would begin following such
a four hour period, regardless of whether or not the engine had been
shut down. Thus, the ``clock'' for monitors that are required to run
once per driving cycle would be reset to run again (in the same key-on
engine start or trip) once the engine has been operated beyond four
hours continuously. This would avoid an unnecessary delay in detection
of malfunctions simply because the heavy-duty vehicle operator has
elected to leave the vehicle running continuously for an entire day or
days at a time.
Manufacturers may request Administrator approval to define
monitoring conditions that are not encountered during the FTP cycle. In
evaluating the manufacturer's request, the Administrator will consider
the degree to which the requirement to run

[[Page 3211]]

during the FTP cycle restricts in-use monitoring, the technical
necessity for defining monitoring conditions that are not encountered
during the FTP cycle, data and/or an engineering evaluation submitted
by the manufacturer which demonstrate that the component/system does
not normally function, or monitoring is otherwise not feasible, during
the FTP cycle, and, where applicable, the ability of the manufacturer
to demonstrate that the monitoring conditions will satisfy the minimum
acceptable in-use monitor performance ratio requirement as defined below.
ii. In-Use Performance Tracking Monitoring Conditions
In addition to the general monitoring conditions above, we are
proposing that manufacturers be required to implement software
algorithms in the OBD system to individually track and report in-use
performance of the following monitors in the standardized format
specified in section II.E:
? Diesel NMHC converting catalyst(s)
? Diesel NO_X converting catalyst(s)
? Gasoline catalyst(s)
? Exhaust gas sensor(s)
? Gasoline evaporative system
? Exhaust gas recirculation (EGR) system
? Variable valve timing (VVT) system
? Gasoline secondary air system
? Diesel particulate filter system
? Diesel boost pressure control system
? Diesel NO_X adsorber(s)
The OBD system is not required to track and report in-use
performance for monitors other than those specifically identified above.
iii. In-Use Performance Ratio Requirement
We are also proposing that, for all 2013 and subsequent model year
engines, manufacturers be required to define monitoring conditions
that, in addition to meeting the general monitoring conditions, ensure
that certain monitors yield an in-use performance ratio (which monitors
and the details that define the performance ratio are defined in
section II.E) that meets or exceeds the minimum acceptable in-use
monitor performance ratio for in-use vehicles. We are proposing a
minimum acceptable in-use monitor performance ratio of 0.100 for all
monitors specifically required to track in-use performance. This means
that the monitors listed in section II.A.3.ii above must run and make
valid diagnostic decisions during 10 percent of the vehicle's trips. We
intend to work with industry during the initial years of implementation
to gather data on in-use performance ratios and may revise this ratio
lower as appropriate depending on what we learn.
Note that manufacturers may not use the calculated ratio (or any
element thereof), or any other indication of monitor frequency, as a
monitoring condition for a monitor. For example, the manufacturer would
not be allowed to use a low ratio to enable more frequent monitoring
through diagnostic executive priority or modification of other monitoring
conditions, or to use a high ratio to enable less frequent monitoring.
4. Determining the Proper OBD Malfunction Criteria
For determining the malfunction criteria for diesel engine monitors
associated with an emissions threshold (see sections II.B and II.C for
more on emissions thresholds), we are proposing that manufacturers be
required to determine the appropriate emissions test cycle such that
the most stringent monitor would result. In general, we believe that
manufacturers can make this determination based on engineering
judgement, but there may be situations where testing would be required
to make the determination. We do not necessarily anticipate challenging
a manufacturer's determination of which test cycle to use. Nonetheless,
the manufacturer should be prepared, perhaps with test data, to justify
their determination.
We are also proposing that, for engines equipped with emission
controls that experience infrequent regeneration events (e.g., a DPF
and/or a NO_X adsorber), a manufacturer must adjust the
emission test results for monitors that are required to indicate a
malfunction before emissions exceed a certain emission threshold.\17\
For each such monitor, the manufacturer would have to adjust the
emission result as done in accordance with the provisions of section
86.004-28(i) with the component for which the malfunction criteria are
being established having been deteriorated to the malfunction threshold.
As proposed, the adjusted emission value must be used for purposes of
determining whether or not the applicable emission threshold is exceeded.
---------------------------------------------------------------------------

\17\ See proposed Sec. 86.010-18(f).
---------------------------------------------------------------------------

While we believe that this adjustment process for monitors of
systems that experience infrequent regeneration events makes sense and
would result in robust monitors, we also believe that it could prove to
be overly burdensome for manufacturers. For example, a NO_X
adsorber threshold being evaluated by running an FTP using a
``threshold'' part (i.e., a NO_X adsorber deteriorated such
that tailpipe emissions are at the applicable thresholds) may be
considered acceptable provided the NO_X adsorber does not
regenerate during the test, but it may be considered unacceptable if
the NO_X adsorber does happen to regenerate during the test.
This could happen because emissions would be expected to increase
slightly during the regeneration event thereby causing emissions to be
slightly above the applicable threshold. This would require the
manufacturer to recalibrate the NO_X adsorber monitor to
detect at a lower level of deterioration to ensure that a regeneration
event would not cause an exceedance of the threshold during an
emissions test. After such a recalibration, the emissions occurring
during the regeneration event would be lower than before because the
new ``threshold'' NO_X adsorber would have a slightly higher
conversion efficiency. We are concerned that manufacturers may find
themselves in a difficult iterative process calibrating such monitors
that, in the end, will not be correspondingly more effective.
For this reason, we request comment regarding the burden associated
with the need to consider regeneration events in determining compliance
with emissions thresholds. We also request comment on how to address
any environmental concern versus the burden. Would it perhaps be best
to simply use the emissions adjustments that are determined in
accordance with section 86.004-28(i)? Is it necessary to even consider
regeneration emissions when determining emission threshold compliance
or is it perhaps best to ignore regeneration events in determining
threshold calibrations?

B. Monitoring Requirements and Timelines for Diesel-Fueled/Compression-
Ignition Engines

Table II.B-1 summarizes the proposed diesel fueled compression
ignition emissions thresholds at which point a component or system has
failed to the point of requiring an illuminated MIL and a stored DTC.
More detail regarding the specific monitoring requirements, implementation
schedules, and liabilities can be found in the sections that follow.

[[Page 3212]]

Table II.B-1.--Proposed Emissions Thresholds for Diesel Fueled CI Engines over 14,000 Pounds
----------------------------------------------------------------------------------------------------------------
Component/monitor MY NMHC CO NOX PM
----------------------------------------------------------------------------------------------------------------
NMHC catalyst system...................................... 2010-2012 2.5x ....... ....... ...........
2013+ 2x ....... ....... ...........
NOX catalyst system....................................... 2010+ ....... ....... +0.3 ...........
DPF system................................................ 2010-2012 2.5x ....... ....... 0.05/+0.04
2013+ 2x ....... ....... 0.05/+0.04
Air-fuel ratio sensors upstream........................... 2010-2012 2.5x 2.5x +0.3 0.03/+0.02
2013+ 2x 2x +0.3 0.03/+0.02
Air-fuel ratio sensors downstream......................... 2010-2012 2.5x ....... +0.3 0.05/+0.04
2013+ 2x ....... +0.3 0.05/+0.04
NOX sensors............................................... 2010+ ....... ....... +0.3 0.05/+0.04
``Other monitors'' with emissions thresholds (see section 2010-2012 2.5x 2.5x +0.3 0.03/+0.02
II.B)....................................................
2013+ 2x 2x +0.3 0.03/+0.02
----------------------------------------------------------------------------------------------------------------
Notes: MY=Model Year; 2.5x means a multiple of 2.5 times the applicable emissions standard or family emissions
limit (FEL); +0.3 means the standard or FEL plus 0.3; 0.05/+0.04 means an absolute level of 0.05 or an
additive level of the standard or FEL plus 0.04, whichever level is higher; not all proposed monitors have
emissions thresholds but instead rely on functionality and rationality checks as described in section II.D.4.

There are exceptions to the emissions thresholds shown in Table
II.B-1 whereby a manufacturer can demonstrate that emissions do not
exceed the threshold even when the component or system is non-
functional at which point a functional check would be allowed.
Note that, in general, the monitoring strategies designed to meet
the requirements discussed below should not involve the alteration of
the engine control system or the emissions control system such that
tailpipe emissions would increase. We do not want emissions to
increase, even for short durations, for the sole purpose of monitoring
the systems intended to control emissions. The Administrator would
consider such monitoring strategies on a case-by-case basis taking into
consideration the emissions impact and duration of the monitoring
event. However, much effort has been expended in recent years to
minimize engine operation that results in increased emissions and we
encourage manufacturers to develop monitoring strategies that do not
require alteration of the basic control system.
1. Fuel System Monitoring
a. Background
The fuel system of a diesel engine is an essential component of the
engine's emissions control system. Proper delivery of fuel--quantity,
pressure, and timing--can play a crucial role in maintaining low
engine-out emissions. The performance of the fuel system is also
critical for aftertreatment device control strategies. As such,
thorough monitoring of the fuel system is an essential element in an
OBD system. The fuel system is primarily comprised of a fuel pump, fuel
pressure control device, and fuel injectors. Additionally, the fuel
system generally has sophisticated control strategies that utilize one
or more feedback sensors to ensure the proper amount of fuel is being
delivered to the cylinders. While gasoline engines have undergone
relatively minor hardware changes (but substantial fine-tuning in the
control strategy and feedback inputs), diesel engines have more
recently undergone substantial changes to the fuel system hardware and
now incorporate more refined control strategies and feedback inputs.
For diesel engines, a substantial change has occurred in recent
years as manufacturers have transitioned to new high-pressure fuel
systems. One of the most widely used is a high-pressure common-rail
fuel injection system, which is generally comprised of a high-pressure
fuel pump, a fuel rail pressure sensor, a common fuel rail that feeds
all injectors, individual fuel injectors that directly control fuel
injection quantity and timing for each cylinder, and a closed-loop
feedback system that uses the fuel rail pressure sensor to achieve the
commanded fuel rail pressure. Unlike older style fuel systems where
fuel pressure was mechanically linked to engine speed (and thus, varied
from low to high as engine speed increased), common-rail systems are
capable of controlling fuel pressure independent of engine speed. This
increase in fuel pressure control allows greater flexibility in
optimizing the performance and emission characteristics of the engine.
The ability of the system to generate high pressure independent of
engine speed also improves fuel delivery at low engine speeds.
Precise control of the fuel injection timing is crucial for optimal
engine and emission performance. As injection timing is advanced (i.e.,
fuel injection occurs earlier), hydrocarbon (HC) emissions and fuel
consumption are decreased but oxides of nitrogen (NO_X)
emissions are increased. As injection timing is retarded (i.e., fuel
injection occurs later), NO_X emissions can be reduced but HC
emissions, particulate matter (PM) emissions, and fuel consumption
increase. Most modern diesel fuel systems even provide engine
manufacturers with the ability to separate a single fuel injection
event into discrete events such as pilot (or pre) injection, main
injection, and post injection.
Given the important role that modern diesel fuel systems play in
emissions control, malfunctions or deterioration that would affect the
fuel pressure control, injection timing, pilot/main/post injection
timing or quantity, or ability to accurately perform rate-shaping could
lead to substantial increases in emissions (primarily NO_X or
PM), often times with an associated change in fuel consumption.
b. Fuel System Monitoring Requirements
We are proposing that the OBD system monitor the fuel delivery
system to verify that it is functioning properly. The fuel system
monitor would be required to monitor for malfunctions in the injection
pressure control, injection quantity, injection timing, and feedback
control (if equipped). The individual electronic components (e.g.,
actuators, valves, sensors, pumps) that are used in the fuel system and
not specifically addressed in this section shall be monitored in
accordance with the comprehensive component requirements in section II.D.4.
i. Fuel System Pressure Control
We are proposing that the OBD system continuously monitor the fuel
system's ability to control to the desired fuel pressure. The OBD
system would have to detect a malfunction of the fuel system's pressure
control system when

[[Page 3213]]

the pressure control system is unable to maintain an engine's emissions
at or below the emissions thresholds for ``other monitors'' as shown in
Table II.B-1. For engines in which no failure or deterioration of the
fuel system pressure control could result in an engine's emissions
exceeding the applicable emissions thresholds, the OBD system would be
required to detect a malfunction when the system has reached its control
limits such that the commanded fuel system pressure cannot be delivered.
ii. Fuel System Injection Quantity
We are proposing that the OBD system detect a malfunction of the
fuel injection system when the system is unable to deliver the
commanded quantity of fuel necessary to maintain an engine's emissions
at or below the emissions thresholds for ``other monitors'' as shown in
Table II.B-1. For engines in which no failure or deterioration of the
fuel injection quantity could result in an engine's emissions exceeding
the applicable emissions thresholds, the OBD system would be required
to detect a malfunction when the system has reached its control limits
such that the commanded fuel quantity cannot be delivered.
iii. Fuel System Injection Timing
We are proposing that the OBD system detect a malfunction of the
fuel injection system when the system is unable to deliver fuel at the
proper crank angle/timing (e.g., injection timing too advanced or too
retarded) necessary to maintain an engine's emissions at or below the
emissions thresholds for ``other monitors'' as shown in Table II.B-1.
For engines in which no failure or deterioration of the fuel injection
timing could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system would be required to detect a
malfunction when the system has reached its control limits such that
the commanded fuel injection timing cannot be achieved.
iv. Fuel System Feedback Control
If the engine is equipped with feedback control of the fuel system
(e.g., feedback control of pressure or pilot injection quantity), we
are proposing that the OBD system detect a malfunction when and if:
? The system fails to begin feedback control within a
manufacturer specified time interval;
? A failure or deterioration causes open loop or default operation; or
? Feedback control has used up all of the adjustment allowed
by the manufacturer.
A manufacturer may temporarily disable monitoring for malfunctions
where the feedback control has used up all of the adjustment allowed by
the manufacturer during conditions that the monitor cannot distinguish
robustly between a malfunctioning system and a properly operating
system. To do so, the manufacturer would be required to submit data
and/or engineering analyses demonstrating that the control system, when
operating as designed on an engine with all emission controls working
properly, routinely operates during these conditions with all of the
adjustment allowed by the manufacturer used up. In lieu of detecting,
with a fuel system specific monitor, when the system fails to begin
feedback control within a manufacturer specified time interval and/or
when a failure or deterioration causes open loop or default operation,
the OBD system may monitor the individual parameters or components that
are used as inputs for fuel system feedback control provided that the
monitors detect all malfunctions related to feedback control.
c. Fuel System Monitoring Conditions
The OBD system would be required to monitor continuously for
malfunctions of the fuel pressure control and feedback control.
Manufacturers would be required to define the monitoring conditions for
malfunctions of the injection quantity and injection timing such that
the minimum performance ratio requirements discussed in section II.E
would be met.
d. Fuel System MIL Illumination and DTC Storage
We are proposing the general MIL illumination and DTC storage
requirements as discussed in section II.A.2.
2. Engine Misfire Monitoring
a. Background
Misfire, the lack of combustion in the cylinder, causes increased
engine-out hydrocarbon emissions. On gasoline engines, misfire results
from the absence of spark, poor fuel metering, and poor compression.
Further, misfire can be intermittent on gasoline engines (e.g., the
misfire only occurs under certain engine speeds or loads).
Consequently, our existing under 14,000 pound OBD regulation requires
continuous monitoring for misfire malfunctions on gasoline engines.
In contrast, manufacturers have historically maintained that a
diesel engine with traditional diesel technology misfires only due to
poor compression (e.g., worn valves or piston rings, improper injector
or glow plug seating). They have also maintained that, when poor
compression results in a misfiring cylinder, the cylinder will misfire
under all operating conditions rather than only some operating
conditions. For that reason, our existing under 14,000 pound OBD
regulation has not required continuous monitoring for misfire
malfunctions on diesel engines.
However, with the increased use of EGR and its use to varying
degrees at different speeds and load, and with emerging technologies
such as homogeneous charge compression ignition (HCCI), we believe that
the conventional wisdom regarding diesel engines and misfires no longer
holds true. These newer technologies may indeed result in misfires that
are intermittent, spread out among various cylinders, and that only
happen at certain speeds and loads.
b. Misfire Monitoring Requirements
We are proposing that the OBD system monitor the engine for misfire
causing excess emissions. The OBD system must be capable of detecting
misfire occurring in one or more cylinders. To the extent possible
without adding hardware for this specific purpose, the OBD system must
also identify the specific misfiring cylinder. If more than one
cylinder is continuously misfiring, a separate DTC must be stored
indicating that multiple cylinders are misfiring. When identifying
multiple cylinder misfire, the OBD system is not required to also
identify each of the continuously misfiring cylinders individually
through separate DTCs.
For 2013 and subsequent model year engines, we are proposing a more
stringent requirement that the OBD system detect a misfire malfunction
causing emissions to exceed the emissions thresholds for ``other
monitors'' as shown in Table II.B-1. This requirement to detect engine
misfire prior to exceeding an emissions threshold would apply only to
those engines equipped with sensors capable of detecting combustion or
combustion quality (e.g., cylinder pressure sensors used in homogeneous
charge compression ignition (HCCI) control systems). Engines without
such sensors would have to detect only when one or more cylinders are
continually misfiring.
To determine what level of misfire would cause emissions to exceed
the applicable emissions thresholds, we are proposing that
manufacturers determine

[[Page 3214]]

the percentage of misfire evaluated in 1000 revolution increments that
would cause emissions from an emission durability demonstration engine
to exceed the emissions thresholds if the percentage of misfire were
present from the beginning of the test. To establish this percentage of
misfire, the manufacturer would utilize misfire events occurring at
equally spaced, complete engine cycle intervals, across randomly
selected cylinders throughout each 1000-revolution increment. If this
percentage of misfire is determined to be lower than one percent, the
manufacturer may set the malfunction criteria at one percent. Any
malfunction should be detected if the percentage of misfire established
via this testing is exceeded regardless of the pattern of misfire
events (e.g., random, equally spaced, continuous).
The manufacturer may employ other revolution increments besides the
1000 revolution increment being proposed. To do so, the manufacturer
would need to demonstrate that the strategy would be equally effective
and timely in detecting misfire.
c. Engine Misfire Monitoring Conditions
For engines without combustion sensors, we are proposing that the
OBD system monitor for misfire during engine idle conditions at least
once per drive cycle in which the monitoring conditions for misfire are
met. The manufacturer would be required to define monitoring
conditions, supported by manufacturer-submitted data and/or engineering
analyses, that demonstrate that the monitoring conditions: are
technically necessary to ensure robust detection of malfunctions (e.g.,
avoid false passes and false detection of malfunctions); require no
more than 1000 cumulative engine revolutions; and, do not require any
single continuous idle operation of more than 15 seconds to make a
determination that a malfunction is present (e.g., a decision can be made
with data gathered during several idle operations of 15 seconds or less).
For 2013 and subsequent model year engines with combustion sensors,
we are proposing that the OBD system continuously monitor for misfire
under all positive torque engine speeds and load conditions. If a
monitoring system cannot detect all misfire patterns under all positive
torque engine speeds and load conditions, the manufacturer may request
that the Administrator approve the monitoring system nonetheless. In
evaluating the manufacturer's request, the Administrator would consider
the following factors: the magnitude of the region(s) in which misfire
detection is limited; the degree to which misfire detection is limited
in the region(s) (i.e., the probability of detection of misfire
events); the frequency with which said region(s) are expected to be
encountered in-use; the type of misfire patterns for which misfire
detection is troublesome; and demonstration that the monitoring
technology employed is not inherently incapable of detecting misfire
under required conditions (i.e., compliance can be achieved on other
engines). The evaluation would be based on the following misfire
patterns: equally spaced misfire occurring on randomly selected
cylinders; single cylinder continuous misfire; and, paired cylinder
(cylinders firing at the same crank angle) continuous misfire.
d. Engine Misfire MIL Illumination and DTC Storage
For engines without combustion sensors, we are proposing the
general MIL illumination and DTC storage requirements as discussed in
section II.A.2.
For 2013 and subsequent model year engines with combustion sensors,
we are proposing that, after four detections of the percentage of
misfire that would cause emissions to exceed the applicable emissions
thresholds during a single driving cycle, a pending DTC would be
stored. If a pending DTC is stored, the OBD system would be required to
illuminate the MIL and store a MIL--on DTC if the percentage of misfire
is again exceeded four times during either: the driving cycle
immediately following the storage of the pending DTC, regardless of the
conditions encountered during the driving cycle; or, the next driving
cycle in which similar conditions are encountered to the engine
conditions that occurred when the pending DTC was stored.\18\ For
erasure of the pending DTC, we are proposing if, by the end of the next
driving cycle in which similar conditions have been encountered to the
engine conditions that occurred when the pending DTC was stored without
an exceedance of the specified percentage of misfire, the pending DTC
may be erased. The pending DTC may also be erased if similar conditions
are not encountered during the next 80 driving cycles immediately
following initial detection of the malfunction.
---------------------------------------------------------------------------

\18\ ``Similar conditions,'' as used in conjunction with misfire
and fuel system monitoring, means engine conditions having an engine
speed within 375 rpm, load conditions within 20 percent, and the
same warm up status (i.e., cold or hot) as existing during the
applicable previous problem detection. The Administrator may approve
other definitions of similar conditions based on comparable
timeliness and reliability in detecting similar engine operation.
---------------------------------------------------------------------------

We are proposing some specific items with respect to freeze frame
storage associated with engine misfire. The OBD system shall store and
erase freeze frame conditions either in conjunction with storing and
erasing a pending DTC or in conjunction with storing a MIL--on DTC and
erasing a MIL--on DTC. In addition to those proposed requirements
discussed in section II.A.2, we are proposing that, if freeze frame
conditions are stored for a malfunction other than a misfire
malfunction when a DTC is stored, the previously stored freeze frame
information shall be replaced with freeze frame information regarding
the misfire malfunction (i.e., the misfire's freeze frame information
should take precedence over freeze frames for other malfunctions).
Further, we are proposing that, upon detection of misfire, the OBD
system store the following engine conditions: engine speed, load, and
warm up status of the first misfire event that resulted in the storage
of the pending DTC.
Lastly, we are proposing that the MIL may be extinguished after
three sequential driving cycles in which similar conditions have been
encountered without an exceedance of the specified percentage of misfire.
3. Exhaust Gas Recirculation (EGR) System Monitoring
a. Background
Exhaust gas recirculation (EGR) systems are currently being used by
many heavy-duty engine manufacturers to meet the 2.5 g/bhp-hr
NO_X+NMHC standard for 2004 and later model year engines. (65
FR 59896) EGR reduces NO_X emissions in several ways. First,
the recirculated exhaust gases dilute the intake air--i.e., oxygen in
the fresh air is displaced with relatively non-reactive exhaust gases--
which, in turn, results in less oxygen to form NO_X. Second,
EGR absorbs heat from the combustion process which reduces combustion
chamber temperatures which, in turn, reduces NO_X formation.
The amount of heat absorbed from the combustion process is a function
of EGR flow rate and recirculated gas temperature, both of which are
controlled to minimize NO_X emissions. An EGR cooler can be
added to the EGR system to lower the recirculated gas temperature which
further enhances NO_X control. We fully expect that 2007 and
later model year engines will continue to make use of cooled EGR systems.
While in theory the EGR system simply routes some exhaust gas back
to the intake, production systems can be complex and involve many
components to ensure accurate control of EGR flow

[[Page 3215]]

to maintain acceptable PM and NO_X emissions while minimizing
effects on fuel economy. To control EGR flow rates, EGR systems
normally use the following components: an EGR valve, valve position
sensor, boost pressure sensor, intake temperature sensor, intake
(fresh) airflow sensor, and tubing or piping to connect the various
components of the system. EGR temperature sensors and exhaust
backpressure sensors can also be used. Additionally, some systems use a
variable geometry turbocharger to provide the backpressure necessary to
drive the EGR flow. Therefore, EGR is not a stand alone emission
control device. Rather, it is carefully integrated with the air
handling system (turbocharging and intake cooling) to control
NO_X while not adversely affecting PM emissions and fuel economy.
b. EGR System Monitoring Requirements
We are proposing that the OBD system monitor the EGR system on
engines so equipped for low EGR flow rate, high EGR flow rate, and slow
EGR flow response malfunctions. For engines so equipped, we are
proposing that the EGR feedback control be monitored. Also, for engines
equipped with EGR coolers (e.g., heat exchangers), the OBD system would
have to monitor the cooler for malfunctions associated with
insufficient EGR cooling. The individual electronic components (e.g.,
actuators, valves, sensors) that are used in the EGR system would be
monitored in accordance with the comprehensive component requirements
presented in section II.D.4.
i. EGR Low Flow Malfunctions
We are proposing that the OBD system detect a malfunction prior to
a decrease from the manufacturer's specified EGR flow rate that would
cause an engine's emissions to exceed the emissions thresholds for
``other monitors'' as shown in Table II.B-1. For engines in which no
failure or deterioration of the EGR system that causes a decrease in
flow could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when the system has reached its control limits such that it cannot
increase EGR flow to achieve the commanded flow rate.
ii. EGR High Flow Malfunctions
We are proposing that the OBD system detect a malfunction of the
EGR system, including a leaking EGR valve--i.e., exhaust gas flowing
through the valve when the valve is commanded closed--prior to an
increase from the manufacturer's specified EGR flow rate that would
cause an engine's emissions to exceed the emissions thresholds for
``other monitors'' as shown in Table II.B-1. For engines in which no
failure or deterioration of the EGR system that causes an increase in
flow could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when the system has reached its control limits such that it cannot
reduce EGR flow to achieve the commanded flow rate.
iii. EGR Slow Response Malfunctions
We are proposing that the OBD system detect a malfunction of the
EGR system prior to any failure or deterioration in the capability of
the EGR system to achieve the commanded flow rate within a
manufacturer-specified time that would cause an engine's emissions to
exceed the emissions thresholds for ``other monitors'' as shown in
Table II.B-1. The OBD system would have to monitor both the capability
of the EGR system to respond to a commanded increase in flow and the
capability of the EGR system to respond to a commanded decrease in flow.
iv. EGR Feedback Control
We are proposing that the OBD system on any engine equipped with
feedback control of the EGR system (e.g., feedback control of flow,
valve position, pressure differential across the valve via intake
throttle or exhaust backpressure), detect a malfunction when and if:
? The system fails to begin feedback control within a
manufacturer specified time interval;
? A failure or deterioration causes open loop or default operation; or
? Feedback control has used up all of the adjustment allowed
by the manufacturer.
v. EGR Cooler Performance
We are proposing that the OBD system detect a malfunction of the
EGR cooler prior to a reduction from the manufacturer's specified
cooling performance that would cause an engine's emissions to exceed
the emissions thresholds for ``other monitors'' as shown in Table II.B-
1. For engines in which no failure or deterioration of the EGR cooler
could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when the system has no detectable amount of EGR cooling.
c. EGR System Monitoring Conditions
We are proposing that the OBD system monitor continuously for low
EGR flow, high EGR flow, and feedback control malfunctions.
Manufacturers would be required to define the monitoring conditions for
EGR slow response malfunctions such that the minimum performance ratio
requirements discussed in section II.E would be met with the exception
that monitoring must occur every time the monitoring conditions are met
during the driving cycle in lieu of once per driving cycle as required
for most monitors. For purposes of tracking and reporting as required
in section II.E, all monitors used to detect EGR slow response
malfunctions must be tracked separately but reported as a single set of
values as specified in section II.E.\19\
---------------------------------------------------------------------------

\19\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

Manufacturersmay temporarily disable the EGR system check under
specific conditions (e.g., when freezing may affect performance of the
system). To do so, the manufacturer would be required to submit data
and/or engineering analyses that demonstrate that a reliable check
cannot be made when these specific conditions exist.
d. EGR System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.
4. Turbo Boost Control System Monitoring
a. Background
Turbochargers are used on internal combustion engines to enhance
performance by increasing the density of the intake air. Some of the
benefits of turbocharging include increased horsepower, improved fuel
economy, and decreased exhaust smoke. Most modern diesel engines take
advantage of these benefits and are equipped with turbocharging
systems. Moreover, smaller turbocharged diesel engines can be used in
place of larger non-turbocharged engines to achieve the desired engine
performance characteristics.

[[Page 3216]]

Exhaust gases passing through the turbine cause it to spin which,
in turn, causes an adjacent centrifugal pump on the same rotating shaft
to spin. The spinning pump serves to compress the intake air thereby
increasing its density. Typically, a boost pressure sensor is located
in the intake manifold to provide a feedback signal of the current
intake manifold pressure. As turbo speed (boost) increases, the
pressure in the intake manifold also increases.
Proper boost control is essential to optimize emission levels. Even
short periods of over-or under-boost can result in undesired air-fuel
ratio excursions and corresponding emission increases. Additionally,
the boost control system directly affects exhaust and intake manifold
pressures. Another critical emission control system, EGR, is very
dependent on these two pressures and generally uses the differential
between them to force exhaust gas into the intake manifold. If the
boost control system is not operating correctly, the exhaust or intake
pressures may not be as expected and the EGR system may not function as
designed. In high-pressure EGR systems, higher exhaust pressures will
generate more EGR flow and, conversely, lower pressures will reduce EGR
flow. A malfunction that causes excessive exhaust pressures (e.g.,
wastegate stuck closed at high engine speed) can produce higher EGR
flowrates at high load conditions and have a negative impact on emissions.
Manufacturers commonly use charge air coolers to maximize the
benefits of turbocharging and to control NO_X emissions. As
the turbocharger compresses the intake air, the temperature of that
intake air increases. This increasing air temperature causes the air to
expand, which conflicts with one of the goals of turbocharging which is
to increase charge air density. Charge air coolers are used to exchange
heat between the compressed air and ambient air (or coolant) and cool
the compressed air. Accordingly, a decrease in charge air cooler
performance can affect emissions by causing higher intake air
temperatures that can lead to higher combustion temperatures and higher
NO_X emissions.
One drawback of turbocharging is known as turbo lag. Turbo lag
occurs when the driver attempts to accelerate quickly from a low engine
speed. Since the turbocharger is a mechanical device, a delay exists
from the driver demand for more boost until the exhaust flow can
physically speed up the turbocharger enough to deliver that boost. In
addition to a negative effect on driveability and performance, improper
fueling (e.g., over-fueling) during this lag can cause emission
increases (typically PM).
To decrease the effects of turbo lag, manufacturers design turbos
that spool up quickly at low engine speeds and low exhaust flowrates.
However, designing a turbo that will accelerate quickly from a low
engine speed but will not result in an over-speed/over-boost condition
at higher engine speeds is challenging. That is, as the engine speed
and exhaust flowrates near their maximum, the turbo speed increases to
levels that cause excessive boost pressures and heat that could lead to
engine or turbo damage. To prevent excessive turbine speeds and boost
pressures at higher engine speeds, a wastegate is often used to bypass
part of the exhaust stream around the turbocharger. The wastegate valve
is typically closed at lower engine speeds so that all exhaust is
directed through the turbocharger, thus providing quick response from
the turbocharger when the driver accelerates quickly from low engine
speeds. The wastegate is then opened at higher engine speeds to prevent
engine or turbo damage from an over-speed condition.
An alternative to a wastegate is the variable geometry
turborcharger (VGT). To prevent over-boost conditions and to decrease
turbo lag, VGTs are designed such that the geometry of the turbocharger
changes with engine speed. While various physical mechanisms are used
to achieve the variable geometry, the overall result is essentially the
same. At low engine speeds, the exhaust gas into the turbo is
restricted in a manner that maximizes the use of the available energy
to spin the turbo. This allows the turbo to spool up quickly and
provide good acceleration response. At higher engine speeds, the turbo
geometry changes such that exhaust gas flow into the turbo is not as
restricted. In this configuration, more exhaust can flow through the
turbocharger without causing an over-speed condition. The advantage
that VGTs offer compared to a waste-gated turbocharger is that all
exhaust flow is directed through the turbocharger under all operating
conditions. This can be viewed as maximizing the use of the available
exhaust energy.
b. Turbo Boost Control System Monitoring Requirements
We are proposing that the OBD system monitor the boost pressure
control system on engines so equipped for under and over boost
malfunctions. For engines equipped with variable geometry turbochargers
(VGT), the OBD system would have to monitor the VGT system for slow
response malfunctions. For engines equipped with charge air cooler
systems, the OBD system would have to monitor the charge air cooler
system for cooling system performance malfunctions. The individual
electronic components (e.g., actuators, valves, sensors) that are used
in the boost pressure control system shall be monitored in accordance
with the comprehensive component requirements in section II.D.4.
i. Turbo Underboost Malfunctions
We are proposing that the OBD system detect a malfunction of the
boost pressure control system prior to a decrease from the
manufacturer's commanded boost pressure that would cause an engine's
emissions to exceed the emissions thresholds for ``other monitors'' as
shown in Table II.B-1. For engines in which no failure or deterioration
of the boost pressure control system that causes a decrease in boost
could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system must detect a malfunction when the
system has reached its control limits such that it cannot increase
boost to achieve the commanded boost pressure.
ii. Turbo Overboost Malfunctions
We are proposing that the OBD system detect a malfunction of the
boost pressure control system prior to an increase from the
manufacturer's commanded boost pressure that would cause an engine's
emissions to exceed the emissions thresholds for ``other monitors'' as
shown in Table II.B-1. For engines in which no failure or deterioration
of the boost pressure control system that causes an increase in boost
could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system must detect a malfunction when the
system has reached its control limits such that it cannot decrease
boost to achieve the commanded boost pressure.
iii. VGT Slow Response Malfunctions
We are proposing that the OBD system detect a malfunction prior to
any failure or deterioration in the capability of the VGT system to
achieve the commanded turbocharger geometry within a manufacturer-
specified time that would cause an engine's emissions to exceed the
emissions thresholds for ``other monitors'' as shown in Table II.B-1.
For engines in which no failure or deterioration of the VGT system
response could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system must detect a malfunction of the
VGT system when proper functional response

[[Page 3217]]

of the system to computer commands does not occur.
iv. Turbo Boost Feedback Control Malfunctions
We are proposing that, for engines equipped with feedback control
of the boost pressure system--e.g., control of VGT position, turbine
speed, manifold pressure--the OBD system shall detect a malfunction
when and if:
? The system fails to begin feedback control within a
manufacturer specified time interval;
? A failure or deterioration causes open loop or default operation; or
? Feedback control has used up all of the adjustment allowed
by the manufacturer.
v. Charge Air Undercooling Malfunctions
We are proposing that the OBD system detect a malfunction of the
charge air cooling system prior to a decrease from the manufacturer's
specified cooling rate that would cause an engine's emissions to exceed
the emissions thresholds for ``other monitors'' as shown in Table II.B-
1. For engines in which no failure or deterioration of the charge air
cooling system that causes a decrease in cooling performance could
result in an engine's emissions exceeding the applicable emissions
thresholds, the OBD system must detect a malfunction when the system
has no detectable amount of charge air cooling.
c. Turbo Boost Control System Monitoring Conditions
We are proposing that the OBD system monitor continuously for
underboost and overboost malfunctions and for boost feedback control
malfunctions. Manufacturers would be required to define the monitoring
conditions for VGT slow response malfunctions such that the minimum
performance ratio requirements discussed in section II.E would be met
with the exception that monitoring must occur every time the monitoring
conditions are met during the driving cycle in lieu of once per driving
cycle as required for most monitors. For purposes of tracking and
reporting as required in section II.E, all monitors used to detect VGT
slow response malfunctions malfunctions must be tracked separately but
reported as a single set of values as discussed in section II.E.\20\
---------------------------------------------------------------------------

\20\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

d. Turbo Boost MIL Illumination and DTC Storage
We are proposing the general MIL illumination and DTC storage
requirements as discussed in section II.A.2.
5. Non-Methane Hydrocarbon (NMHC) Converting Catalyst Monitoring
a. Background
Diesel oxidation catalysts (DOCs) have been used on some nonroad
diesel engines since the 1960s and on some diesel trucks and buses in
the U.S. since the early 1990s. DOCs are generally used for converting
HC and carbon monoxide (CO) emissions to water and CO₂ via
an oxidation process. Current DOCs can also be used to convert PM
emissions. DOCs may also be used in conjunction with other
aftertreatment emission controls--such as NO_X adsorber
systems, selective catalytic reduction (SCR) systems, and PM filters--
to improve their performance and/or clean up certain reducing agents
that might slip through the system (e.g., the urea used in urea SCR
systems).
b. NMHC Converting Catalyst Monitoring Requirements
We are proposing that the OBD system monitor the NMHC converting
catalyst(s) for proper NMHC conversion capability. We are also
proposing that each catalyst that converts NMHC be monitored either
individually or in combination with others. For engines equipped with
catalyzed diesel particulate filters (CDPFs) that convert NMHC
emissions, the catalyst function of the CDPF must be monitored in
accordance with the CDPF monitoring requirements in section II.B.8.
i. NMHC Converting Catalyst Conversion Efficiency
We are proposing that the OBD system detect an NMHC catalyst
malfunction when the catalyst conversion capability decreases to the
point that NMHC emissions exceed the emissions thresholds for ``NMHC
catalysts'' as shown in Table II.B-1. If no failure or deterioration of
the catalyst NMHC conversion capability could result in an engine's
NMHC emissions exceeding the applicable emissions thresholds, the OBD
system would have to detect a malfunction when the catalyst has no
detectable amount of NMHC conversion capability.
ii. Other Aftertreatment Assistance Functions
For catalysts used to generate an exotherm to assist CDPF
regeneration, we are proposing that the OBD system detect a malfunction
when the catalyst is unable to generate a sufficient exotherm to
achieve that regeneration. For catalysts used to generate a feedgas
constituency to assist SCR systems (e.g., to increase NO₂
concentration upstream of an SCR system), the OBD system would have to
detect a malfunction when the catalyst is unable to generate the
necessary feedgas constituents for proper SCR system operation. For
catalysts located downstream of a CDPF and used to convert NMHC
emissions during a CDPF regeneration event, the OBD system would be
required to detect a malfunction when the catalyst has no detectable
amount of NMHC conversion capability.
c. NMHC Converting Catalyst Monitoring Conditions
Manufacturers would be required to define the monitoring conditions
for NMHC converting catalyst malfunctions such that the minimum
performance ratio requirements discussed in section II.E would be met.
For purposes of tracking and reporting as discussed in section II.E,
all monitors used to detect NMHC converting catalyst malfunctions must
be tracked separately but reported as a single set of values as
discussed in section II.E.\21\
---------------------------------------------------------------------------

\21\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

d. NMHC Converting Catalyst MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage discussed in section II.A.2. Note that the monitoring
method for the catalyst(s) must be capable of detecting all instances,
except diagnostic self-clearing, when a catalyst DTC has been cleared
but the catalyst has not been replaced (e.g., catalyst over temperature
histogram approaches are not acceptable).\22\
---------------------------------------------------------------------------

\22\ For gasoline catalyst monitoring, manufacturers generally
use what is called an exponentially weighted moving average (EWMA)
approach to making decisions about the catalyst's pass/fail status.
This approach monitors the catalyst and ``saves'' that information.
The next time it monitors the catalyst, it saves that information
along with the previous information, placing a higher weighting on
the most recent information. This is done every time the OBD system
monitors the catalyst and the EWMA saves six or seven monitoring
events before making a decision. Importantly, once there exists six
or seven pieces of information, every monitoring event can result in
a decision because the EWMA is always using the previous six or
seven events. Unfortunately, if a service technician clears the data
with a scan tool, it is going to take six or seven monitoring events
before the catalyst monitor can make a decision on the pass/fail
status of the catalyst. So, we want to be sure that, in addition to
the EWMA aspect of the catalyst monitor, there exists a way of
determining quickly that someone has cleared the data but perhaps
did not actually repair the catalyst. This is required to help
prevent against DTC clearing without fixing a failed catalyst as a
means of passing an inspection & maintenance test.

---------------------------------------------------------------------------

[[Page 3218]]

6. Selective Catalytic Reduction (SCR) and Lean NO_X Catalyst
Monitoring
a. Background
Selective Catalytic Reduction (SCR) catalysts that use ammonia as a
NO_X reductant have been used for stationary source
NO_X control for a number of years. Frequently, urea is used
as the source of ammonia for SCR catalysts, and such systems are
commonly referred to as Urea SCR systems. In recent years, considerable
effort has been invested in developing urea SCR systems that could be
applied to heavy-duty diesel vehicles with low sulfur diesel fuel. We
now expect that urea SCR systems will be introduced in Europe to comply
with the EURO IV heavy-duty diesel emission standards. Such systems
have been introduced in the past year by some heavy-duty diesel engine
manufacturers both in Europe and in Japan.
SCR catalyst systems require an accurate urea control system to
inject precise amounts of reductant. An injection rate that is too low
may result in lower NO_X conversions while an injection that
is too high may release unwanted ammonia emissions--referred to as
ammonia slip--to the atmosphere. In general, ammonia to NO_X
ratios of around 1:1 are used to provide the highest NO_X
conversion rates with minimal ammonia slip. Therefore, injecting just
the right amount of ammonia appropriate for the amount of
NO_X in the exhaust is very important. This can be
challenging in a highway application because on-road diesel engines
operate over a variety of speeds and loads. This makes the use of
closed-loop feedback systems for reductant metering very attractive.
This can be achieved, for example, with a dedicated NO_X
sensor in the exhaust so that the NO_X concentration can be
accurately known. With an accurate fast response NO_X sensor,
closed-loop control of the ammonia injection can be used to achieve and
maintain the desired ammonia/NO_X ratios in the SCR catalyst
for the high NO_X conversion efficiencies necessary to achieve
the 2010 emission standards under various engine operating conditions.
Some have estimated that achieving the 2010 NO_X emission
standards with SCR systems will require NO_X sensors that can
measure NO_X levels accurately in the 20 to 40 ppm range with
little cross sensitivity to ammonia. Some in industry have even stated
a desire for accuracy in the two to three ppm range. Suppliers have
been developing NO_X sensors capable of measuring
NO_X in the 0 to 100 ppm range with +/-5 ppm accuracy which
we believe will be available by 2010.\23\ Regarding cross-sensitivity
to ammonia, work has been done that indicates ammonia and
NO_X measurements can be independently measured by
conditioning the output signal.\24\ This signal conditioning method
resulted in a linear output for both ammonia and NO_X from
the NO_X sensor downstream of the catalyst.
---------------------------------------------------------------------------

\23\ Draft Technical Support Document, HDOBD NPRM, EPA420-D-06-
006, Docket ID# EPA-HQ-OAR-2005-0047-0008.
\24\ Schaer, C. M., Onder, C. H., Geering, H. P., and Elsener,
M., ``Control of a Urea SCR Catalytic Converter System for a Mobile
Heavy-Duty Diesel Engine,'' SAE Paper 2003-01-0776 which may be
obtained from Society of Automotive Engineers International, 400
Commonwealth Dr., Warrendale, PA, 15096-0001.
---------------------------------------------------------------------------

For SCR systems, closed-loop control of the reductant injection may
require the use of two NO_X sensors. The first NO_X
sensor would be located upstream of the catalyst and the reductant
injection point would be used for measuring the engine-out
NO_X emissions and determining the amount of reductant
injection needed to reduce emissions. The second NO_X sensor
located downstream of the catalyst would be used for measuring the
amount of ammonia and NO_X emissions exiting the catalyst and
providing feedback to the reductant injection control system. If the
downstream NO_X sensor detects too much NO_X
emissions exiting the catalyst, the control system can inject higher
quantities of reductant. Conversely, if the downstream NO_X
sensor detects too much ammonia slip exiting the catalyst, the control
system can decrease the amount of reductant injection.
In addition to exhaust NO_X levels, another important
parameter for achieving high NO_X conversion rates with
minimum ammonia slip is catalyst temperature. SCR catalysts have a
defined temperature range where they are most effective. For example,
platinum catalysts are effective between 175 and 250 degrees Celsius,
vanadium catalysts are effective between 300 and 450 degrees Celsius,
and zeolite catalysts are most effective between 350 and 600 degrees
Celsius. To determine exhaust catalyst temperature for reductant
control purposes, manufacturers are likely to use temperature sensors
placed in the exhaust system. We project that only one temperature
sensor positioned just downstream of the SCR system will be utilized
for reductant injection control purposes.
Production SCR catalyst systems may also contain auxiliary
catalysts to improve the overall emissions control capability of the
system. An oxidation catalyst is often positioned downstream of the SCR
catalyst to help control ammonia slip on systems without closed-loop
control of ammonia injection. The use of a ``guard'' catalyst could
allow higher ammonia injection levels, thereby increasing the
NO_X conversion efficiency without releasing un-reacted
ammonia into the exhaust. The guard catalyst can also reduce HC and CO
emission levels and diesel odors. However, increased N2O emissions may
occur and NO_X emission levels may actually increase if too
much ammonia is oxidized in the catalyst. Some SCR systems may also
include an oxidation catalyst upstream of the SCR catalyst and urea
injection point to generate NO2 for lowering the effective operating
temperature and/or volume of the SCR catalyst. Studies have indicated
that increasing the NO2 content in the exhaust stream can reduce the
SCR temperature requirements by about 100 degrees Celsius.\25\ This
``pre-oxidation'' catalyst also has the added benefit of reducing HC
emissions.
---------------------------------------------------------------------------

\25\ Walker, A. P., Chandler, G. R., Cooper, B. J., et al., ``An
Integrated SCR and Continuously Regenerating Trap System to Meet
Future NO_X and PM Legislation,'' SAE Paper 2000-01-0188
which may be obtained from Society of Automotive Engineers
International, 400 Commonwealth Dr., Warrendale, PA, 15096-0001.
---------------------------------------------------------------------------

b. SCR and Lean NO_X Catalyst Monitoring Requirements
We are proposing that the OBD system monitor SCR catalysts and lean
NO_X catalysts for proper conversion capability. We are also
proposing that each catalyst that converts NO_X be monitored
either individually or in combination with others. For engines equipped
with SCR systems or other catalyst systems that utilize an active/
intrusive reductant injection (e.g., active lean NO_X
catalysts utilizing diesel fuel

[[Page 3219]]

injection), the OBD system would be required to monitor the active/
intrusive reductant injection system for proper performance. The
individual electronic components (e.g., actuators, valves, sensors,
heaters, pumps) in the active/intrusive reductant injection system must
be monitored in accordance with the comprehensive component
requirements in section II.D.4.
i. Catalyst Conversion Efficiency Malfunctions
We are proposing that the OBD system detect a catalyst malfunction
when the catalyst conversion capability decreases to the point that
would cause an engine's NO_X emissions to exceed any of the
applicable emissions thresholds for ``NO_X Catalyst Systems''
as shown in Table II.B-1. If no failure or deterioration of the
catalyst NO_X conversion capability could result in an
engine's NO_X emissions exceeding any of the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when the catalyst has no detectable amount of NO_X conversion
capability.
ii. Active/Intrusive Reductant Injection System Malfunctions
Specific to SCR and other active/intrusive reductant injection
system performance, we are proposing that the OBD system detect a
malfunction prior to any failure or deterioration of the system to
regulate reductant delivery properly (e.g., urea injection, separate
injector fuel injection, post injection of fuel, air assisted
injection/mixing) that would cause an engine's NO_X emissions
to exceed any of the applicable emissions thresholds for
``NO_X Catalyst Systems'' as shown in Table II.B-1. As above,
if no failure or deterioration of the reductant delivery system could
result in an engine's NO_X emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when the system has reached its control limits such that it is no
longer able to deliver the desired quantity of reductant.
If the system uses a reductant other than the fuel used for the
engine or uses a reservoir/tank for the reductant that is separate from
the fuel tank used for the engine, the OBD system must detect a
malfunction when there is no longer sufficient reductant available
(e.g., the reductant tank is empty). If the system uses a reservoir/
tank for the reductant that is separate from the fuel tank used for the
engine, the OBD system must detect a malfunction when an improper
reductant is used in the reductant reservoir/tank (e.g., the reductant
tank is filled with something other than the proper reductant).
iii. SCR and Lean NO_X Catalyst Feedback Control System
Malfunctions
If the engine is equipped with feedback control of the reductant
injection, we are proposing that the OBD system detect a malfunction
when and if:
? The system fails to begin feedback control within a
manufacturer specified time interval;
? A failure or deterioration causes open loop or default operation; or
? Feedback control has used up all of the adjustment allowed
by the manufacturer.
c. SCR and Lean NO_X Catalyst Monitoring Conditions
Manufacturers would be required to define the monitoring conditions
for catalyst conversion efficiency malfunctions such that the minimum
performance ratio requirements discussed in section II.E would be met.
For purposes of tracking and reporting as required in section II.E, all
monitors used to detect catalyst conversion efficiency malfunctions
must be tracked separately but reported as a single set of values as
specified in section II.E.\26\ We are also proposing that the OBD
system monitor continuously for active/intrusive reductant injection
system malfunctions. Manufacturers would be required to monitor
continuously the active/intrusive reductant delivery system.
---------------------------------------------------------------------------

\26\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

d. SCR and Lean NO_X Catalyst MIL Illumination and DTC Storage
We are proposing the general MIL illumination and DTC storage
requirements presented in section II.A.2 with the exception of active/
intrusive reductant injection related malfunctions. If the OBD system
is capable of discerning that a system malfunction is being caused by
an empty reductant tank, the manufacturer may delay illumination of the
MIL if the vehicle is equipped with an alternative indicator for
notifying the vehicle operator of the malfunction. The manufacturer
would be required to demonstrate that: The alternative indicator is of
sufficient illumination and location to be readily visible to the
operator under all lighting conditions; and the alternative indicator
provides equivalent assurance that a vehicle operator will be promptly
notified; and, that corrective action would be undertaken. If the
vehicle is not equipped with an alternative indicator and the MIL
illuminates, the MIL may be immediately extinguished and the
corresponding DTC erased once the OBD system has verified that the
reductant tank has been properly refilled and the MIL has not been
illuminated for any other type of malfunction. The Administrator may
approve other strategies that provide equivalent assurance that a
vehicle operator will be promptly notified and that corrective action
will be undertaken.
The monitoring method for the catalyst(s) would have to be capable
of detecting all instances, except diagnostic self-clearing, when a
catalyst DTC has been cleared but the catalyst has not been replaced
(e.g., catalyst over temperature histogram approaches are not acceptable).
7. NO_X Adsorber System Monitoring
a. Background
NO_X adsorbers, or lean NO_X traps (LNT), work
to control NO_X emissions by storing NO_X on the
surface of the catalyst during the lean engine operation typical of
diesel engines and then by undergoing subsequent brief rich
regeneration events where the NO_X is released and reduced
across a precious metal catalyst.
NO_X adsorber systems generally consist of a conventional
three-way catalyst function (e.g., platinum) with NO_X
storage components (i.e., adsorbents) incorporated into the washcoat.
Three-way catalysts convert NO_X emissions as well as HC and
CO emissions (hence the name three-way) by promoting oxidation of HC
and CO to H₂O and CO₂ using the oxidation
potential of the NO_X pollutant and, in the process, reducing
the NO_X emissions to nitrogen, N₂. Said another
way, three-way catalysts work with exhaust conditions where the net
oxidizing and reducing chemistry of the exhaust is approximately equal,
allowing the catalyst to promote complete oxidation/reduction reactions
to the desired exhaust components of CO₂, H₂O,
and N₂. The oxidizing potential in the exhaust comes from
NO_X emissions and any feedgas oxygen (O₂) not
consumed during combustion. The reducing potential in the exhaust

[[Page 3220]]

comes from HC and CO emissions, which represent products of incomplete
combustion. Operation of the engine to ensure that the oxidizing and
reducing potential of the combustion and exhaust conditions is
precisely balanced is referred to as stoichiometric engine operation.
Because diesel engines run lean of stoichiometric operation, the
NO_X emissions are stored, or absorbed--via chemical reaction
with alkaline earth metals such as barium nitrate in the washcoat--and
then released during rich operation for conversion to N₂.
This NO_X release during rich operation is referred to as a
regeneration event. The rich operating conditions required for
NO_X regeneration, which generally last for several seconds,
are typically achieved using a combination of intake air throttling (to
reduce the amount of intake air), exhaust gas recirculation, and post-
combustion fuel injection.
NO_X adsorber systems have demonstrated NO_X
reduction efficiencies from 50 percent to in excess of 90 percent. This
efficiency has been found to be highly dependent on the fuel sulfur
content because NO_X adsorbers are extremely sensitive to
sulfur. The NO_X adsorption material has an even greater
affinity for sulfur compounds than NO_X. Thus, sulfur
compounds can saturate the adsorber and limit the number of active
sites for NO_X adsorption, thereby lowering the
NO_X reduction efficiency. Accordingly, low sulfur fuel is
required to achieve the greatest NO_X reduction efficiencies.
Although new adsorber washcoat materials are being developed with a
higher resistance to sulfur poisoning and ultra-low sulfur fuel will be
the norm by 2010, NO_X adsorber systems will still need to
purge the stored sulfur from the storage bed by a process referred to
as desulfation. Because the desulfation process takes longer (e.g.,
several minutes) and requires more fuel and heat than the
NO_X regeneration step, permanent thermal degradation of the
NO_X adsorber and fuel economy penalties may result from
desulfation events happening with excessive frequency. However, if
desulfation is not done frequently enough, NO_X storage
capacity would be compromised and fuel economy penalties would be
incurred from excessive attempts at NO_X regeneration.
In order to achieve and maintain high NO_X conversion
efficiencies while limiting negative impacts on fuel economy and
driveability, vehicles with NO_X adsorber systems will
require precise air/fuel control in the engine and in the exhaust
stream. Diesel manufacturers are expected to utilize NO_X
sensors and temperature sensors to provide the most precise closed-loop
control for the NO_X adsorber system. If NO_X
sensors are not used to control the NO_X adsorber system,
manufacturers could use wide-range air-fuel (A/F) sensors located
upstream and downstream of the adsorber as a substitute. However, A/F
sensors cannot provide an instantaneous indication of tailpipe
NO_X levels, which would allow the control system to
precisely determine when the adsorber system is filled to capacity and
regeneration should be initiated. If A/F sensors are used in lieu of
NO_X sensors, an estimation of engine-out NO_X
emissions and their subsequent storage in the NO_X adsorber
can be achieved indirectly through modeling.
b. NO_X Adsorber System Monitoring Requirements
We are proposing that the OBD system monitor the NO_X
adsorber on engines so equipped for proper performance. For engines
equipped with active/intrusive injection (e.g., in-exhaust fuel and/or
air injection) to achieve NO_X regeneration, the OBD system
would have to monitor the active/intrusive injection system for proper
performance. The individual electronic components (e.g., injectors,
valves, sensors) that are used in the active/intrusive injection system
would have to be monitored in accordance with the comprehensive
component requirements in section II.D.4.
i. NO_X Adsorber Capability Malfunctions
We are proposing that the OBD system detect a NO_X
adsorber malfunction when its capability--i.e., its combined adsorption
and conversion capability--decreases to the point that would cause an
engine's NO_X emissions to exceed the applicable emissions
thresholds for ``NO_X Catalyst Systems'' as shown in Table
II.B-1. If no failure or deterioration of the NO_X adsorber
capability could result in an engine's NO_X emissions
exceeding the applicable emissions thresholds, the OBD system would
have to detect a malfunction when the system has no detectable amount
of NO_X adsorber capability.
ii. Active/Intrusive Reductant Injection System Malfunctions
For NO_X adsorber systems that use active/intrusive
injection (e.g., in-cylinder post fuel injection, in-exhaust air-
assisted fuel injection) to achieve desorption of the NO_X
adsorber, the OBD system would have to detect a malfunction if any
failure or deterioration of the injection system's ability to properly
regulate injection causes the system to be unable to achieve desorption
of the NO_X adsorber.
iii. NO_X Adsorber Feedback Control System Malfunctions
If the engine is equipped with feedback control of the reductant
injection (e.g., feedback control of injection quantity, time), we are
proposing that the OBD system detect a malfunction when and if:
? The system fails to begin feedback control within a
manufacturer specified time interval;
? A failure or deterioration causes open loop or default operation; or
? Feedback control has used up all of the adjustment allowed
by the manufacturer.
c. NO_X Adsorber System Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for NO_X adsorber capability malfunctions such
that the minimum performance ratio requirements discussed in section
II.E would be met. For purposes of tracking and reporting as required
in section II.E, all monitors used to detect NO_X adsorber
capability malfunctions must be tracked separately but reported as a
single set of values as specified in section II.E.\27\ We are also
proposing that the OBD system monitor continuously for active/intrusive
reductant injection and feedback control system malfunctions.
---------------------------------------------------------------------------

\27\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

d. NO_X Adsorber System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage discussed in section II.A.2.
8. Diesel Particulate Filter (DPF) System Monitoring
a. Background
Diesel particulate filters control diesel PM by capturing the soot
(solid carbon) portion of PM in a filter media, typically a ceramic
wall flow substrate, and then by oxidizing (burning) it in the oxygen-
rich atmosphere of diesel exhaust.\28\ In aggregate over a driving
cycle, the PM must be burned at a rate equal to or

[[Page 3221]]

greater than its accumulation rate, or the DPF will clog. Given low
sulfur diesel fuel (diesel fuel with a sulfur content of 15 ppm or
lower), highly active catalytic metals (e.g., platinum) can be used to
promote soot oxidation. This method of PM filter regeneration, called
passive regeneration, is the primary means of soot oxidation that we
project industry will use in 2007/2010.
---------------------------------------------------------------------------

\28\ See ``Regulatory Impact Analysis: Heavy-Duty Engine and
Vehicle Standards and Highway Diesel Fuel Sulfur Control
Requirements;'' EPA420-R-00-026; December 2000 at Chapter III for a
more complete description of DPFs.
---------------------------------------------------------------------------

The DPF technology has proven itself in tens of thousands of
retrofit applications where low sulfur diesel fuel is already
available. More than a million light-duty passenger cars in Europe now
have diesel particulate filters. DPFs are considered the most effective
control technology for the reduction of particulate emissions and can
typically achieve PM reductions in excess of 90 percent.
In order to maintain the performance of the DPF and the engine, the
trapped PM must be periodically removed before too much particulate is
accumulated and exhaust backpressure reaches unacceptable levels. The
process of periodically removing accumulated PM from the DPF is known
as ``regeneration'' and is very important for maintaining low PM
emission levels. DPF regeneration can be passive (i.e., occur
continuously during regular operation of the filter), active (i.e.,
occur on a controlled, periodic basis after a predetermined quantity of
particulates have been accumulated), or a combination of the two. With
passive regeneration, the oxidizing catalyst material on the DPF
substrate serves to lower the temperature for oxidizing PM. This allows
the DPF to continuously oxidize trapped PM material during normal
driving. In contrast, active systems utilize an external heat source--
such as an electric heater or fuel burner--to facilitate DPF
regeneration. We are projecting that virtually all DPF systems will
have some sort of active regeneration mechanism as a backup mechanism
should operating conditions not be conducive for passive regeneration.
One of the key considerations for a DPF regeneration control system
is the amount of soot quantity that is stored in the DPF (often called
soot loading). If too much soot is stored when regeneration is
activated, the soot can burn uncontrollably and DPF substrate could be
damaged via melting or cracking. Conversely, activating regeneration
when there is too little trapped soot will not ensure good combustion
propagation which would effectively waste the energy (fuel) used to
initiate the regeneration. Another important consideration in the
control system design is the fuel economy penalty involved with DPF
regeneration. Prolonged operation with high backpressures in the
exhaust and regenerations occurring too frequently are both detrimental
to fuel economy and DPF durability. Therefore, DPF system designers
will need to carefully balance the regeneration frequency with various
conflicting factors. To optimize the trap regeneration for these design
factors, the DPF regeneration control system is projected to
incorporate both pressure sensors and temperature sensors to model soot
loading and other phenomena.\29\ Through the information provided by
these sensors, designers can optimize the DPF for high effectiveness
and maximum durability while minimizing fuel economy and performance
penalties.
---------------------------------------------------------------------------

\29\ Salvat, O., Marez, P., and Belot, G., ``Passenger Car
Serial Application of a Particulate Filter System on a Common Rail
Direct Injection Diesel Engine,'' SAE Paper 2000-01-0473 which may
be obtained from Society of Automotive Engineers International, 400
Commonwealth Dr., Warrendale, PA, 15096-0001.
---------------------------------------------------------------------------

b. DPF System Monitoring Requirements
We are proposing that the OBD system monitor the DPF on engines so-
equipped for proper performance.\30\ For engines equipped with active
regeneration systems that utilize an active/intrusive injection (e.g.,
in-exhaust fuel injection, in-exhaust fuel/air burner), the OBD system
would have to monitor the active/intrusive injection system for proper
performance. The individual electronic components (e.g., injectors,
valves, sensors) that are used in the active/intrusive injection system
must be monitored in accordance with the comprehensive component
requirements in section II.D.4.
---------------------------------------------------------------------------

\30\ Note that these requirements would also apply to a
catalyzed diesel particulate filter (CDPF). We use the more common
term DPF throughout this discussion.
---------------------------------------------------------------------------

i. PM Filtering Performance
We are proposing that the OBD system detect a malfunction prior to
a decrease in the filtering capability of the DPF (e.g., cracking,
melting, etc.) that would cause an engine's PM emissions to exceed the
applicable emissions thresholds for ``DPF Systems'' as shown in Table
II.B-1. If no failure or deterioration of the PM filtering performance
could result in an engine's PM emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when no detectable amount of PM filtering occurs.
ii. DPF Regeneration Frequency Malfunctions--Too Frequent
We are proposing that the OBD system detect a malfunction when the
DPF regeneration frequency increases from--i.e., occurs more often
than--the manufacturer's specified regeneration frequency to a level
such that it would cause an engine's NMHC emissions to exceed the
applicable emissions threshold for ``DPF Systems'' as shown in Table
II.B-1. If no such regeneration frequency exists that could cause NMHC
emissions to exceed the applicable emission threshold, the OBD system
would have to detect a malfunction when the PM filter regeneration
frequency exceeds the manufacturer's specified design limits for
allowable regeneration frequency.
iii. DPF Incomplete Regeneration Malfunctions
We are proposing that the OBD system detect a regeneration
malfunction when the DPF does not properly regenerate under
manufacturer-defined conditions where regeneration is designed to occur.
iv. DPF NMHC Conversion Efficiency Malfunctions
We are proposing that, for any DPF that serves to convert NMHC
emissions, the OBD system must monitor the NMHC converting function of
the DPF and detect a malfunction when the NMHC conversion capability
decreases to the point that NMHC emissions exceed the NMHC threshold
for ``DPF Systems'' as shown in Table II.B-1. If no failure or
deterioration of the NMHC conversion capability could result in NMHC
emissions exceeding the applicable NMHC threshold, the OBD system would
have to detect a malfunction when the system has no detectable amount
of NMHC conversion capability.
v. DPF Missing Substrate Malfunctions
We are proposing that the OBD system detect a malfunction if either
the DPF substrate is completely destroyed, removed, or missing, or if
the DPF assembly has been replaced with a muffler or straight pipe.
vi. DPF Active/Intrusive Injection System Malfunctions
We are proposing that, for systems that utilize active/intrusive
injection (e.g., in-cylinder post fuel injection, in-exhaust air-
assisted fuel injection) to achieve DPF regeneration, the OBD system
detect a malfunction if any

[[Page 3222]]

failure or deterioration of the injection system's ability to properly
regulate injection causes the system to be unable to achieve DPF
regeneration.
vii. DPF Regeneration Feedback Control System Malfunctions
We are proposing that, if the engine is equipped with feedback
control of the DPF regeneration (e.g., feedback control of oxidation
catalyst inlet temperature, PM filter inlet or outlet temperature, in-
cylinder or in-exhaust fuel injection), the OBD system must detect a
malfunction when and if:
? The system fails to begin feedback control within a
manufacturer specified time interval;
? A failure or deterioration causes open loop or default operation; or
? Feedback control has used up all of the adjustment allowed
by the manufacturer.
c. DPF System Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for all DPF related malfunctions such that the minimum
performance ratio requirements discussed in section II.E would be met
with the exception that monitoring must occur every time the monitoring
conditions are met during the driving cycle rather than once per
driving cycle as required for most monitors. For purposes of tracking
and reporting as required in section II.E, all monitors used to detect
all DPF related malfunctions would have to be tracked separately but
reported as a single set of values as specified in section II.E.\31\
---------------------------------------------------------------------------

\31\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

d. DPF System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.
9. Exhaust Gas Sensor Monitoring
a. Background
Exhaust gas sensors (e.g., oxygen sensors, wide-range air-fuel (A/
F) sensors, NO_X sensors) are important to the emission
control system of vehicles. These sensors are used for enhancing the
performance of several emission control technologies (e.g., catalysts,
EGR systems). We expect that both oxygen sensors and wide range A/F
sensors may be used by heavy-duty manufacturers to optimize their
emission control technologies. We would expect that, in addition to
their emissions control functions, these sensors will also be used to
satisfy many of the proposed HDOBD monitoring requirements, such as
fuel system monitoring, catalyst monitoring, and EGR system monitoring.
NO_X sensors may also be used for optimization of several
diesel emission control technologies, such as NO_X adsorbers
and selective catalytic reduction (SCR) systems. Since an exhaust gas
sensor can be a critical component of a vehicle's fuel and emission
control system, the proper performance of this component needs to be
assured to maintain low emissions. The reliance on these sensors for
emissions control and OBD monitoring makes it important that any
malfunction that adversely affects the performance of any of these
sensors be detected by the OBD system.
b. Exhaust Gas Sensor Monitoring Requirements
We are proposing that the OBD system monitor all exhaust gas
sensors (e.g., oxygen, air-fuel ratio, NO_X) used either for
emission control system feedback (e.g., EGR control/feedback, SCR
control/feedback, NO_X adsorber control/feedback), or as a
monitoring device, for proper output signal, activity, response rate,
and any other parameter that can affect emissions. For engines equipped
with heated exhaust gas sensors, the OBD system would have to monitor
the heater for proper performance.
i. Air/Fuel Ratio Sensor Malfunctions
For all air/fuel ratio sensors, we are proposing the following:
? Circuit malfunctions: The OBD system must detect
malfunctions of the sensor caused by either a lack of circuit
continuity or out-of-range values.
? Feedback malfunctions: The OBD system must detect a
malfunction of the sensor when a sensor failure or deterioration causes
an emissions control system--e.g., the EGR, SCR, or NO_X
adsorber systems--to stop using that sensor as a feedback input (e.g.,
causes default or open-loop operation).
? Monitoring capability: To the extent feasible, the OBD
system must detect a malfunction of the sensor when the sensor output
voltage, resistance, impedance, current, amplitude, activity, offset,
or other characteristics are no longer sufficient for use as an OBD
system monitoring device (e.g., for catalyst, EGR, SCR, or
NO_X adsorber monitoring).
Specifically for sensors located upstream of an aftertreatment
device, we are proposing the following:
? Sensor performance malfunctions: The OBD system must
detect a malfunction prior to any failure or deterioration of the
sensor voltage, resistance, impedance, current, response rate,
amplitude, offset, or other characteristic(s) that would cause an
engine's emissions to exceed the applicable emissions thresholds for
``Other Monitors'' as shown in Table II.B-1.
Specifically for sensors located downstream of an aftertreatment
device, we are proposing the following:
? Sensor performance malfunctions: The OBD system must
detect a malfunction prior to any failure or deterioration of the
sensor voltage, resistance, impedance, current, response rate,
amplitude, offset, or other characteristic(s) that would cause an
engine's emissions to exceed the applicable emissions thresholds for
``Air-fuel ratio sensors downstream of aftertreatment devices'' as
shown in Table II.B-1.
ii. NO_X Sensor Malfunctions
For NO_X sensors, we are proposing the following:
? Sensor performance malfunctions: The OBD system must
detect a malfunction prior to any failure or deterioration of the
sensor voltage, resistance, impedance, current, response rate,
amplitude, offset, or other characteristic(s) that would cause an
engine's emissions to exceed the applicable emissions thresholds for
``NO_X sensors'' as shown in Table II.B-1.
? Circuit malfunctions: The OBD system must detect
malfunctions of the sensor caused by either a lack of circuit
continuity or out-of-range values.
? Feedback malfunctions: The OBD system shall detect a
malfunction of the sensor when a sensor failure or deterioration causes
an emission control--e.g., the EGR, SCR, or NO_X adsorber
systems--to stop using that sensor as a feedback input (e.g., causes
default or open-loop operation).
? Monitoring capability: To the extent feasible, the OBD
system must detect a malfunction of the sensor when the sensor output
voltage, resistance, impedance, current, amplitude, activity, offset,
or other characteristics are no longer sufficient for use as an OBD
system monitoring device (e.g., for catalyst, EGR, SCR, or
NO_X adsorber monitoring).

[[Page 3223]]

iii. Other Exhaust Gas Sensor Malfunctions
For other exhaust gas sensors, we are proposing that the
manufacturer submit a monitoring plan to the Administrator for
approval. The Administrator would approve the request upon determining
that the manufacturer has submitted data and an engineering evaluation
that demonstrate that the monitoring plan is as reliable and effective as
the monitoring plan required for air/fuel ratio sensors and NO_X sensors.
iv. Exhaust Gas Sensor Heater Malfunctions
We are proposing that the OBD system detect a malfunction of the
heater performance when the current or voltage drop in the heater
circuit is no longer within the manufacturer's specified limits for
normal operation (i.e., within the criteria required to be met by the
component vendor for heater circuit performance at high mileage). The
manufacturer may use other malfunction criteria for heater performance
malfunctions. To do so, the manufacturer would be required to submit
data and/or engineering analyses that demonstrate that the monitoring
reliability and timeliness would be equivalent to the criteria stated
here. Further, the OBD system would be required to detect malfunctions
of the heater circuit including open or short circuits that conflict
with the commanded state of the heater (e.g., shorted to 12 Volts when
commanded to 0 Volts (ground)).
c. Exhaust Gas Sensor Monitoring Conditions
For exhaust gas sensor performance malfunctions, we are proposing
that manufacturers define the monitoring conditions such that the
minimum performance ratio requirements discussed in section II.E would
be met. For purposes of tracking and reporting as required in section
II.E, all monitors used to detect sensor performance malfunctions would
have to be tracked separately but reported as a single set of values as
specified in section II.E.\32\
---------------------------------------------------------------------------

\32\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

For exhaust gas sensor monitoring capability malfunctions,
manufacturers would have to define the monitoring conditions such that
the minimum performance ratio requirements discussed in section II.E
would be met with the exception that monitoring must occur every time
the monitoring conditions are met during the driving cycle rather than
once per driving cycle as required for most monitors.
For exhaust gas sensor circuit malfunctions and feedback
malfunctions, monitoring must be conducted continuously.
The manufacturer may disable continuous exhaust gas sensor
monitoring when an exhaust gas sensor malfunction cannot be
distinguished from other effects (e.g., disable ``out-of-range low''
monitoring during fuel cut conditions). To do so, the manufacturer
would be required to submit test data and/or engineering analyses that
demonstrate that a properly functioning sensor cannot be distinguished
from a malfunctioning sensor and that the disablement interval is
limited only to that necessary for avoiding a false detection.
For exhaust gas sensor heater malfunctions, manufacturers must
define monitoring conditions such that the minimum performance ratio
requirements discussed in section II.E would be met. Monitoring for
sensor heater circuit malfunctions must be conducted continuously.
d. Exhaust Gas Sensor MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.

C. Monitoring Requirements and Timelines for Gasoline/Spark-Ignition Engines

Table II.C-1 summarizes the proposed gasoline fueled spark ignition
emissions thresholds at which point a component or system has failed to
the point of requiring an illuminated MIL and a stored DTC. Table II.C-
2 summarizes the proposed implementation schedule for these
thresholds--i.e., the proposed certification requirements and in-use
liabilities. More detail regarding the specific monitoring
requirements, implementation schedules, and liabilities can be found in
the sections that follow.

Table II.C-1.--Proposed Emissions Thresholds for Gasoline Fueled SI Engines Over 14,000 Pounds
----------------------------------------------------------------------------------------------------------------
Component/Monitor MY NMHC CO NOX
----------------------------------------------------------------------------------------------------------------
Catalytic converter system....... 2010+............. 1.75x............. .................. 1.75x
``Other monitors'' with emissions 2010+............. 1.5x.............. 1.5x.............. 1.5x
thresholds (see section II.C).
Evaporative emissions control 2010+............. 0.150 inch leak ..
system.
----------------------------------------------------------------------------------------------------------------
Notes: MY=Model Year; 1.75x means a multiple of 1.75 times the applicable emissions standard; not all proposed
monitors have emissions thresholds but instead rely on functionality and rationality checks as described in
section II.D.4. The evaporative emissions control system threshold is not, technically, an emissions threshold
but rather a leak size that must be detected; nonetheless, for ease we refer to this as the threshold.

There are exceptions to the emissions thresholds shown in Table
II.C-1 whereby a manufacturer can demonstrate that emissions do not
exceed the threshold even when the component or system is non-
functional at which point a functional check would be allowed.
The monitoring requirements described below for gasoline engines
mirror those that are already in place for gasoline engines used in
vehicles under 14,000 pounds. The HD gasoline industry--General Motors
and Ford, as of today \33\--have told us that their preference is to
use essentially the same OBD system on their engines used in both under
and over 14,000 pound vehicles.\34\ In general, we agree with the

[[Page 3224]]

HD gasoline industry on this issue for three reasons:
---------------------------------------------------------------------------

\33\ This is true according to our certification database for
both he 2004 and 2005 model years. Other manufacturers certify
engines that use the Otto cycle, but those engines do not burn
gasoline and instead burn various alternative fuels.
\34\ ``EMA Comments on Proposed HDOBD Requirements for HDGE,''
bullet items 3 and 4; April 28, 2005, Docket ID# EPA-HQ-OAR-2005-0047-0003.
---------------------------------------------------------------------------

? The engines used in vehicles above and below 14,000 pounds
are the same which makes it easy for industry to use the same OBD monitors.
? The existing OBD requirements for engines used in vehicles
below 14,000 pounds have proven effective; and,
? The industry members have more than 10 years experience
complying with the OBD requirements for engines used in vehicles below
14,000 pounds.
As a result, we are proposing requirements that should allow for
OBD system consistency in vehicles under and over 14,000 pounds rather
than proposing requirements that mirror the proposed HD diesel
requirements discussed in section II.B. Nonetheless, the requirements
proposed below are for engine-based OBD monitors only rather than
monitors for the entire powertrain (which would include the
transmission). We are doing this for the same reasons as done for the
proposed diesel OBD requirements in that certification of gasoline
applications over 14,000 pounds, like their diesel counterparts, is
done on an engine basis and not a vehicle basis.
1. Fuel System Monitoring
a. Background
As with diesel engines, the fuel system of a gasoline engine is an
essential component of the engine's emissions control system. Proper
delivery of fuel is essential to maintain stoichiometric operation and
minimize engine out emissions. Proper stoichiometric control is also
critical to maximize catalyst conversion efficiency and reach low
tailpipe emission levels. As such, thorough monitoring of the fuel
system is an essential element in an OBD system.
For gasoline engines, the fuel system generally includes a fuel
pump, fuel pressure regulator, fuel rail, individual injectors for each
cylinder, and a closed-loop feedback control system using oxygen
sensor(s) or air-fuel ratio (A/F) sensor(s). The feedback sensors are
located in the exhaust system and are used to regulate the fuel
injection quantity to achieve a stoichiometric mixture in the exhaust.
If the sensor indicates a rich (or lean) mixture, the system reduces
(or increases) the amount of fuel being injected by applying a short
term correction to the fuel injection quantity calculated for the
current engine operating condition. To account for aging or
deterioration in the system such as reduced injector flow, more
permanent long term corrections are also learned and applied to the
fuel injection quantity for more precise fueling.
For gasoline engines, fuel system monitoring has been implemented
on light-duty vehicles since the 1996 model year and on heavy-duty
vehicles less than 14,000 pounds and the engines used in those vehicles
since the 2004/2005 model year. For heavy-duty gasoline engines used in
vehicles over 14,000 pounds (many of which are the same engine as is
used in vehicles less than 14,000 pounds), the system components and
control strategies are identical to those used in the light-duty and
under 14,000 pound categories. As such, the monitoring requirements
established for engines used in vehicles less than 14,000 pounds can be
directly applied to engines used in vehicles over 14,000 pounds.
b. Fuel System Monitoring Requirements
We are proposing that the fuel system be continuously monitored for
its ability to maintain engine emissions below the applicable emissions
thresholds. Manufacturers would also be required to verify that the
fuel system is in closed-loop operation--e.g., that it is using the
oxygen sensor for feedback control. The individual components of the
fuel system would also be covered by separate monitoring requirements
for oxygen sensors, misfire (for the fuel injectors), and comprehensive
components (in systems such as those with electronically-controlled
variable speed fuel pumps or electronically-controlled fuel pressure
regulators).
i. Fuel System Performance
We are proposing that the OBD system be required to detect a
malfunction of the fuel delivery system (including feedback control
based on a secondary oxygen sensor) when the fuel delivery system is
unable to maintain the engine's emissions at or below the applicable
emissions thresholds for ``Other monitors'' as shown in Table II.C-1.
ii. Fuel System Feedback Control
If the engine is equipped with adaptive feedback control, we are
proposing that the OBD system be required to detect a malfunction when
the adaptive feedback control has used up all of the adjustment allowed
by the manufacturer. However, if the engine is equipped with feedback
control that is based on a secondary oxygen (or equivalent) sensor, the
OBD system would not be required to detect a malfunction of the fuel
system solely when the feedback control based on that secondary oxygen
sensor has used up all of the adjustment allowed by the manufacturer.
For such systems, the OBD system would be required to meet the fuel
system performance requirements presented above.
Additionally, we are proposing that the OBD system be required to
detect a malfunction whenever the fuel control system fails to enter
closed loop operation within a time interval after engine startup. The
manufacturer would be required to submit data and/or engineering
analyses that support their chosen time interval.
Lastly, manufacturers would be allowed to adjust the malfunction
criteria and/or monitoring conditions to compensate for changes in
altitude, temporary introduction of large amounts of purge vapor, or
for other similar identifiable operating conditions when they occur.
c. Fuel System Monitoring Conditions
We are proposing that the OBD system monitor continuously for
malfunctions of the fuel system.
d. Fuel System MIL Illumination and DTC Storage
We are proposing that a pending DTC be stored immediately upon
detecting a malfunction according to the fuel system monitoring
requirements presented in section II.C.1.b (i.e., rather than waiting
until the end of the drive cycle to store the pending DTC). Once a
pending DTC is stored, the OBD system would be required to illuminate
the MIL immediately and store a MIL-on DTC if a malfunction is again
detected during either of the following two events: (1) The drive cycle
immediately following the drive cycle during which the pending DTC was
stored, regardless of the conditions encountered during the drive
cycle; or, (2) on the next drive cycle during which similar conditions
are encountered to those that occurred when the pending DTC was stored.\35\
---------------------------------------------------------------------------

\35\ ``Similar conditions,'' as used in conjunction with misfire
and fuel system monitoring, means engine conditions having an engine
speed within 375 rpm, load conditions within 20 percent, and the
same warm up status (i.e., cold or hot) as existing during the
applicable previous problem detection. The Administrator may approve
other definitions of similar conditions based on comparable
timeliness and reliability in detecting similar engine operation.
---------------------------------------------------------------------------

We are also proposing that the pending DTC may be erased at the end
of the next drive cycle in which similar conditions have been
encountered without detecting a malfunction according to the fuel
system monitoring requirements. The pending DTC may also be erased if
similar conditions are not encountered during the 80 drive cycles
immediately after the initial

[[Page 3225]]

detection of a malfunction for which the pending DTC was set.
We are proposing some specific requirements with respect to storage
of freeze frame information associated with fuel system malfunctions.
First, the OBD system must store and erase freeze frame information
either in conjunction with storing and erasing a pending DTC or in
conjunction with storing and erasing a MIL-on DTC. Second, if freeze
frame information is already stored for a malfunction other than an
engine misfire or fuel system malfunction at the time that a fuel
system DTC is stored, the preexisting freeze frame information must be
replaced with freeze frame information regarding the fuel system
malfunction.
The OBD system would also be required to store the engine speed,
load, and warm up status present when the first fuel system malfunction
is detected that resulted in the storage of the pending DTC. The MIL
may be extinguished after three sequential drive cycles in which
similar conditions have been encountered without detecting a
malfunction of the fuel system.
2. Engine Misfire Monitoring
a. Background
Detecting engine misfire on a gasoline spark ignition engine is
important for two reasons: Its impact on the emissions performance of
the engine and its impact on the durability of the catalytic converter.
Engine misfire has two primary causes: Lack of spark and poor fuel
metering (delivery). When misfire occurs, unburned fuel and air are
pumped out of the engine and into the exhaust system and into the
catalyst. This can increase dramatically the operating temperature of
the catalyst where temperatures can soar to above 900 degrees Celsius.
This problem is usually most severe under high load/high speed engine
operating conditions and can cause irreversible damage to the catalyst.
Though the durability of catalysts has been improving, most are unable
to sustain continuous operation at such high temperatures. Engine
misfire also contributes to poor emissions performance, especially when
the misfire occurs during engine warm-up and the catalyst itself has
not yet reached its operating temperature.
b. Engine Misfire Monitoring Requirements
We are proposing that the OBD system detect both engine misfire
capable of causing catalyst damage and engine misfire capable of
causing poor emissions performance. Additionally, the OBD system would
be required to identify the specific cylinder in which misfire is
occurring and/or if there exists a condition in which more than one
cylinder is misfiring; when identifying a multiple cylinder misfire
condition, the OBD system would not be required to identify
individually each of the misfiring cylinders. We are proposing an
exception to this whereby if more than 90 percent of the detected
misfires are occurring in a single cylinder, the manufacturer may elect
to consider it a single cylinder misfire condition rather than a
multiple cylinder misfire condition. However, we are proposing that, if
two or more cylinders individually have more than 10 percent of the
total number of detected misfires, the manufacturer must consider it a
multiple cylinder misfire condition.
i. Engine Misfire Capable of Causing Catalyst Damage
We are proposing that the manufacturer be required to detect the
percentage of misfire--evaluated in 200 revolution increments--for each
engine speed and load condition that would result in a temperature
capable of damaging the catalyst. For every engine speed and load
condition at which this percentage is determined to be less than five
percent, the manufacturer may set the malfunction criteria at five
percent. The manufacturer may use a longer interval than a 200
revolution increment but only for determining, on a given drive cycle,
the first misfire exceedance; upon detecting the first such exceedance,
the 200 revolution increment must be used. The manufacturer may use a
longer initial interval by submitting data and/or engineering analyses
that demonstrate that catalyst damage would not occur due to
unacceptably high catalyst temperatures before the interval has elapsed.
Further, we are proposing that, for the purpose of establishing the
temperature at which catalyst damage would occur, manufacturers not be
allowed to define the catalyst damaging temperature at a temperature
more severe than what the catalyst system could be operated at for 10
consecutive hours and still meet the applicable standards.
ii. Engine Misfire Causing Poor Emissions Performance
We are proposing that the manufacturer be required to detect the
percentage of misfire--evaluated in 1000 revolution increments--that
would cause emissions to exceed the emissions thresholds for ``Other
monitors'' as shown in Table II.C-1 if that percentage of misfire were
present from the beginning of the test procedure. To establish this
percentage of misfire, the manufacturer would be required to use
misfire events occurring at equally spaced, complete engine cycle
intervals, across randomly selected cylinders throughout each 1000
revolution increment. If this percentage of misfire is determined to be
lower than one percent, the manufacturer may set the malfunction
criteria at one percent. The manufacturer may use a different interval
than a 1000 revolution increment. To do so, the manufacturer would be
required to submit data and/or engineering analyses demonstrating that
the strategy would be equally effective and timely at detecting
misfire. A malfunction must be detected if the percentage of misfire is
exceeded regardless of the pattern of misfire events (e.g., random,
equally spaced, continuous).
c. Engine Misfire Monitoring Conditions
We are proposing that the OBD system monitor continuously to detect
engine misfire under all of the following conditions:
? From no later than the end of the second crankshaft
revolution after engine start;
? During the rise time and settling time as the engine
reaches the desired idle speed immediately following engine start-up
(i.e., ``flare-up'' and ``flare-down''); and,
? Under all positive torque conditions except within the
engine operating region bound by lines connecting the following three
points: An engine speed of 3000 rpm with the engine load at the
positive torque line (i.e., engine load with the transmission in
neutral), an engine speed at the redline rpm with the engine load at
the positive torque line, and an engine speed at the redline rpm with
an engine load at which intake manifold vacuum is four inches of
mercury lower than that at the positive torque line (this would be an
engine load somewhat greater than the engine load at the positive
torque line).\36\
---------------------------------------------------------------------------

\36\ ``Redline engine speed'' is actually defined by the
manufacturer as either the recommended maximum engine speed as
normally displayed on instrument panel tachometers or the engine
speed at which fuel shutoff occurs.
---------------------------------------------------------------------------

If a monitoring system cannot detect all misfire patterns under the
required engine speed and load conditions, the manufacturer may request
approval of the system nonetheless. In evaluating the manufacturer's
request, the Administrator would consider:
? The magnitude of the region(s) in which misfire detection is limited;
? The degree to which misfire detection is limited in those region(s)

[[Page 3226]]

(i.e., the probability of detection of misfire events);
? The frequency with which said region(s) are expected to be
encountered in-use;
? The type of misfire patterns for which misfire detection
is troublesome; and,
? Demonstration that the monitoring technology being used is
not inherently incapable of detecting misfire under the required
conditions (i.e., compliance can be achieved by other manufacturers on
their engines).
The Administrator's evaluation would be based on the following
misfire patterns:
? Equally spaced misfire occurring on randomly selected cylinders;
? Single cylinder continuous misfire; and,
? Paired cylinder (cylinders firing at the same crank angle)
continuous misfire.
Further, a manufacturer may use a monitoring system that has
reduced misfire detection capability during the portion of the first
1000 revolutions after engine start during which a cold start emission
reduction strategy is active that reduces engine torque (e.g., spark
retard strategies). To do so, the manufacturer would be required to
submit data and/or engineering analyses demonstrating that the
probability of detection is greater than or equal to 75 percent during
the worst case condition (i.e., lowest generated torque) for a vehicle
operated continuously at idle (park/neutral idle) on a cold start
between 50 and 86 degrees Fahrenheit and that the technology cannot
reliably detect a higher percentage of the misfire events during these
conditions.
A manufacturer may disable misfire monitoring or use an alternative
malfunction criterion when misfire cannot be distinguished from other
effects. To do so, the manufacturer would be required to submit data
and/or engineering analyses demonstrating that the disablement interval
or period of use of an alternative malfunction criterion is limited
only to that necessary for avoiding a false detection (errors of
commission). Such disablements would be allowed for conditions involving:
? Rough road;
? Fuel cut;
? Gear changes for manual transmission vehicles;
? Traction control or other vehicle stability control
activation such as anti-lock braking or other engine torque
modifications to enhance vehicle stability;
? Off-board control or intrusive activation of vehicle
components or diagnostics during service or assembly plant testing;
? Portions of intrusive evaporative system or EGR
diagnostics that can significantly affect engine stability (i.e., while
the purge valve is open during the vacuum pull-down of a evaporative
system leak check but not while the purge valve is closed and the
evaporative system is sealed or while an EGR diagnostic causes the EGR
valve to be intrusively cycled on and off during positive torque
conditions); or,
? Engine speed, load, or torque transients due to throttle
movements more rapid than occurs over the FTP cycle for the worst case
engine within each engine family.
Additionally, the manufacturer may disable misfire monitoring when
the fuel level is 15 percent or less of the nominal capacity of the
fuel tank, when PTO units are active, or while engine coolant
temperature is below 20 degrees Fahrenheit. For the latter case, the
manufacturer may continue the misfire monitoring disablement until
engine coolant temperature exceeds 70 degrees Fahrenheit provided the
manufacturer can demonstrate that it is necessary.
In general, the Administrator would not approve misfire monitoring
disablement for conditions involving normal air conditioning compressor
cycling from on-to-off or off-to-on, automatic transmission gear shifts
(except for shifts occurring during wide open throttle operation),
transitions from idle to off-idle, normal engine speed or load changes
that occur during the engine speed rise time and settling time (i.e.,
``flare-up'' and ``flare-down'') immediately after engine starting
without any vehicle operator-induced actions (e.g., throttle stabs), or
excess acceleration (except for acceleration rates that exceed the
maximum acceleration rate obtainable at wide open throttle while the
vehicle is in gear due to abnormal conditions such as slipping of a clutch).
Further, the manufacturer may request approval of other misfire
monitoring disablements or use of alternative malfunction criteria for
any other condition. The Administrator would consider such requests on
a case by case basis and will consider whether or not the manufacturer
has demonstrated that the request is based on an unusual or unforeseen
circumstance and that it is applying the best available computer and
monitoring technology.
For engines with more than eight cylinders that cannot meet the
continuous monitoring and detection requirements listed above, a
manufacturer may use alternative misfire monitoring conditions. Any
manufacturer wishing to use alternative misfire monitoring conditions
must submit data and/or an engineering evaluation that demonstrate that
misfire detection throughout the required operating region cannot be
achieved when using proven monitoring technology (i.e., a technology
that provides for compliance with these requirements on other engines)
and provided misfire is detected to the fullest extent permitted by the
technology. However, the misfire detection system would still be
required to monitor during all positive torque operating conditions
encountered during an FTP transient cycle.
d. Engine Misfire MIL Illumination and DTC Storage
Manufacturers may store a general misfire DTC instead of a cylinder
specific DTC under certain operating conditions. Do so shall depend on
the manufacturer submitting data and/or an engineering evaluation that
demonstrate that the specific misfiring cylinder cannot be reliably
identified when the certain operating conditions occur.
i. Engine Misfire Capable of Causing Catalyst Damage
We are proposing that a pending DTC shall be stored immediately if,
during a single drive cycle, the percentage of misfire determined by
the manufacturer as being capable of causing catalyst damage is
exceeded three times when operating in the positive torque region
encountered during an FTP transient cycle or is exceeded on a single
occasion when operating at any other engine speed and load condition in
the positive torque region defined above. Immediately after a pending
DTC is stored, the MIL shall blink once per second at all times while
misfire is occurring during the drive cycle (i.e., the MIL may be
extinguished during those times when misfire is not occurring during
the drive cycle). If, at the time such a catalyst damaging engine
misfire is occurring, the MIL is already illuminated for a malfunction
other than engine misfire, the MIL shall blink similarly while the
engine misfire is occurring and, if the misfire ceases, the MIL shall
stop blinking but shall remain illuminated as commanded by the other
malfunction.
If a pending DTC is stored as described above, the OBD system shall
immediately store a MIL-on DTC if the percentage of misfire determined
by the manufacturer as being capable of causing catalyst damage is
again exceeded one or more times during either: (a) the drive cycle
immediately

[[Page 3227]]

following the storage of the pending DTC, regardless of the conditions
encountered during the drive cycle; or, (b) on the next drive cycle in
which similar conditions are encountered to those that existed when the
pending DTC was stored.
If, during a previous drive cycle, a pending DTC has been stored
associated with detection of an engine misfire capable of causing poor
emissions performance, the OBD system shall immediately store a MIL-on
DTC if the percentage of misfire determined by the manufacturer as
capable of causing catalyst damage is exceeded, regardless of the
conditions encountered.
Upon storage of a MIL-on DTC associated with engine misfire capable
of causing catalyst damage, the MIL shall blink as described above
while the engine misfire is occurring and then shall remain
continuously illuminated if the engine misfire ceases. This MIL
illumination logic shall continue until the requirements for
extinguishing the MIL are met, as described below.
If the engine misfire is not again detected by the end of the next
drive cycle in which similar conditions are encountered to those that
existed when the pending DTC was stored then the pending DTC shall be
erased. The pending DTC may also be erased if similar conditions are
not encountered during the 80 drive cycles subsequent to the initial
malfunction detection.
We are also proposing that engines with fuel shutoff and default
fuel control--that are used to prevent catalyst damage should engine
misfire capable of causing catalyst damage be detected--shall have some
exemptions from these MIL illumination requirements. Most notably, the
MIL is not required to blink while the catalyst damaging misfire is
occurring. Instead, the MIL may simply illuminate in a steady fashion
while the misfire is occurring provided that the fuel shutoff and
default fuel control are activated as soon as the misfire is detected.
Fuel shutoff and default fuel control may be deactivated only to permit
fueling outside of the misfire range. Manufacturers may also
periodically, but not more than once every 30 seconds, deactivate fuel
shutoff and default fuel control to determine if the catalyst damaging
misfire is still occurring. Normal fueling and fuel control may be
resumed if the catalyst damaging misfire is no longer being detected.
Manufacturers may also use a MIL illumination strategy that
continuously illuminates the MIL in lieu of blinking the MIL during
extreme misfire conditions capable of causing catalyst damage (i.e.,
misfire capable of causing catalyst damage that is occurring at all
engine speeds and loads). Manufacturers would be allowed to use such a
strategy only when catalyst damaging misfire levels cannot be avoided
during reasonable driving conditions and the manufacturer can
demonstrate that the strategy will encourage operation of the vehicle
in conditions that will minimize catalyst damage (e.g., at low engine
speeds and loads).
ii. Engine Misfire Causing Poor Emissions Performance
We are proposing that, for a misfire detected within the first 1000
revolutions after engine start during which misfire detection is
active, a pending DTC shall be stored after the first exceedance of the
percentage of misfire determined by the manufacturer as capable of
causing poor emissions performance. If a pending DTC is stored, the OBD
system shall illuminate the MIL and store a MIL-on DTC within 10
seconds if an exceedance of the percentage of misfire is again detected
in the first 1000 revolutions during any subsequent drive cycle,
regardless of the conditions encountered during the driving cycle. The
pending DTC shall be erased at the end of the next drive cycle in which
similar conditions are encountered to those that existed when the
pending DTC was stored provided the specified percentage of misfire is
not again detected. The pending DTC may also be erased if similar
conditions are not encountered during the 80 drive cycles subsequent to
the initial malfunction detection.
For a misfire detected after the first 1000 revolutions following
engine start, a pending DTC shall be stored no later than after the
fourth exceedance--during a single drive cycle--of the percentage of
misfire determined by the manufacturer as being capable of causing poor
emissions performance. If a pending DTC is stored, the OBD system shall
illuminate the MIL and store a MIL-on DTC within 10 seconds if an
exceedance of the percentage of misfire is again detected four times
during: (a) the drive cycle immediately following the storage of the
pending DTC, regardless of the conditions encountered during the drive
cycle; or, (b) on the next drive cycle in which similar conditions are
encountered to those that existed when the pending DTC was stored. The
pending DTC shall be erased at the end of the next drive cycle in which
similar conditions are encountered to those that existed when the
pending DTC was stored provided the specified percentage of misfire is
not again detected. The pending DTC may also be erased if similar
conditions are not encountered during the 80 drive cycles subsequent to
the initial malfunction detection.
We are proposing some specific items with respect to freeze frame
storage associated with engine misfire. The OBD system shall store and
erase freeze frame conditions either in conjunction with storing and
erasing a pending DTC or in conjunction with storing a MIL-on DTC and
erasing a MIL-on DTC. In addition to those proposed requirements
discussed in section II.A.2, we are proposing that, if freeze frame
conditions are stored for a malfunction other than a misfire
malfunction when a DTC is stored, the previously stored freeze frame
information shall be replaced with freeze frame information regarding
the misfire malfunction (i.e., the misfire's freeze frame information
should take precedence over freeze frames for other malfunctions).
Further, we are proposing that, upon detection of misfire, the OBD
system store the following engine conditions: engine speed, load, and
warm up status of the first misfire event that resulted in the storage
of the pending DTC.
Lastly, we are proposing that the MIL may be extinguished after
three sequential driving cycles in which similar conditions have been
encountered without an exceedance of the specified percentage of misfire.
3. Exhaust Gas Recirculation (EGR) Monitoring
a. Background
EGR works to reduce NO_X emissions the same way in
gasoline engines as described earlier for diesel engines. First, the
recirculated exhaust gases dilute the intake air--i.e., oxygen in the
fresh air is displaced with relatively non-reactive exhaust gases--
which, in turn, results in less oxygen to form NO_X. Second,
EGR absorbs heat from the combustion process which reduces combustion
chamber temperatures which, in turn, reduces NO_X formation.
The amount of heat absorbed from the combustion process is a function
of EGR flow rate and recirculated gas temperature, both of which are
controlled to minimize NO_X emissions. EGR systems can
involve many components to ensure accurate control of EGR flow,
including valves, valve position sensors, and actuators.
b. EGR System Monitoring Requirements
We are proposing that the OBD system monitor the EGR system on
engines so equipped for low and high

[[Page 3228]]

flow rate malfunctions. The individual electronic components (e.g.,
actuators, valves, sensors) that are used in the EGR system must be
monitored in accordance with the comprehensive component requirements
in section II.D.4.
i. EGR Low Flow Malfunctions
We are proposing that the OBD system detect a malfunction prior to
a decrease from the manufacturer's specified EGR flow rate that would
cause an engine's emissions to exceed the emissions thresholds for
``other monitors'' as shown in Table II.C-1. For engines in which no
failure or deterioration of the EGR system that causes a decrease in
flow could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when the system has reached its control limits such that it cannot
increase EGR flow to achieve the commanded flow rate.
ii. EGR High Flow Malfunctions
We are proposing that the OBD system detect a malfunction of the
EGR system, including a leaking EGR valve--i.e., exhaust gas flowing
through the valve when the valve is commanded closed--prior to an
increase from the manufacturer's specified EGR flow rate that would
cause an engine's emissions to exceed the emissions thresholds for
``other monitors'' as shown in Table II.C-1. For engines in which no
failure or deterioration of the EGR system that causes an increase in
flow could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
when the system has reached its control limits such that it cannot
reduce EGR flow to achieve the commanded flow rate.
c. EGR System Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for EGR system malfunctions such that the minimum
performance ratio requirements discussed in section II.E would be met.
For purposes of tracking and reporting as required in section II.E, all
monitors used to detect EGR low flow and high flow malfunctions must be
tracked separately but reported as a single set of values as specified
in section II.E.\37\
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\37\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

Manufacturers may temporarily disable the EGR system monitor under
conditions when monitoring may not be reliable (e.g., when freezing may
affect performance of the system). Such temporary disablement would be
allowed provided the manufacturer has submitted data and/or an
engineering evaluation that demonstrate that the EGR monitor cannot be
done reliably when these specific conditions exist.
d. EGR System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.
4. Cold Start Emission Reduction Strategy Monitoring
a. Background
The largest portion of exhaust emissions from gasoline engines is
generated during the brief period following startup before the engine
and catalyst have warmed up to their normal operating temperatures. To
meet increasingly stringent emissions standards, manufacturers are
developing hardware and associated control strategies to reduce these
``cold start'' emissions. Most efforts center on reducing catalyst
warm-up time.
A cold catalyst is heated mainly by two mechanisms: heat
transferred from the exhaust gases to the catalyst; and, heat generated
in the catalyst as a result of the exothermic catalytic reactions. Most
manufacturers use substantial spark retard and/or increased idle speed
following a cold engine start, both of which maximize the heat
available in the exhaust gases which, in turn, increases the heat
transfer to the catalyst. Vehicle drivability and engine idle quality
concerns tend to limit the amount of spark retard and/or increased idle
speed that a manufacturer can use to accelerate catalyst warm up. These
strategies or, more correctly, the systems used to employ these
strategies--the ignition system for spark retard and the idle control
system for control of engine speed--are normally monitored only after
engine warm-up. Therefore, any malfunctions that might occur during the
cold start event may not be detected by the OBD system. This could have
significant emissions consequences due to the unknown loss of emissions
control during the time following engine startup.
This concern is exacerbated by the high cost of precious metals--
the platinum group metals (PGM) platinum, palladium, and rhodium--which
motivates industry to minimize their use in catalysts. To compensate
for the resultant reduction in overall catalyst performance,
manufacturers will likely use increasingly more aggressive cold start
emission reduction strategies in an attempt to further reduce cold
start emissions. These strategies must be successful--and be properly
monitored--to meet the more stringent 2008 emissions standards and to
maintain low emissions in-use.
b. Cold Start Emission Reduction Strategy Monitoring Requirements
We are proposing that, if an engine incorporates an engine control
strategy specifically to reduce cold start emissions, the OBD system
must monitor the key components (e.g., idle air control valve), other
than the secondary air system, while the control strategy is active to
ensure that the control strategy is operating properly. Secondary air
systems would have to be monitored separately as discussed in section
II.C.5.
The OBD system would be required to detect a malfunction prior to
any failure or deterioration of the individual components associated
with the cold start emissions reduction control strategy that would
cause an engine's emissions to exceed the emissions thresholds for
``other monitors'' as shown in Table II.C-1. For components where no
failure or deterioration of the component used by the cold start
emission reduction strategy could result in an engine's emissions
exceeding the applicable emissions thresholds, the individual
components would have to be monitored for proper functional response as
described in section II.D.4 while the control strategy is active.
Manufacturers would be required to establish the appropriate
malfunction criteria based on data from one or more representative
engine(s). Further, manufacturers would be required to provide an
engineering evaluation for establishing the malfunction criteria for
the remainder of the manufacturer's product line. An annual evaluation
of these criteria by the Administrator may not be necessary provided
the manufacturer can demonstrate that any technological changes from
one year to the next do not affect the previously approved malfunction
criteria.
c. Cold Start Emission Reduction Strategy Monitoring Conditions
We are proposing that manufacturers define the monitoring conditions for

[[Page 3229]]

malfunctions of the cold start emissions reduction strategy such that
the minimum performance ratio requirements discussed in section II.E
would be met.
d. Cold Start Emission Reduction Strategy MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.
5. Secondary Air System Monitoring
a. Background
Secondary air systems--expected to be used on gasoline engines
only--are used to reduce cold start emissions of hydrocarbons and
carbon monoxide. Many of today's engines operate near stoichiometry
after a cold engine start. However, the future more stringent emission
standards may require the addition of a secondary air system in
combination with a richer than stoichiometric cold start mixture. Such
an approach could quickly warm up the catalyst for improved cold start
emissions performance.
Secondary air systems typically consist of an electric air pump,
various hoses, and check valves to deliver outside air to the exhaust
system upstream of the catalytic converter(s). This system usually
operates only after a cold engine start and usually for only a brief
period of time. When the electric air pump is operating, fresh air is
delivered into the exhaust where it mixes with and ignites any unburned
fuel. This serves to warm up the catalyst far more rapidly than would
otherwise occur. Any problems that might occur in the field--corroded
check valves, damaged tubing and hoses, malfunctioning air switching
valves--could cause cold start emissions performance to suffer.
Therefore, monitoring is needed given the importance of a properly
functioning secondary air system to emissions performance.
b. Secondary Air System Monitoring Requirements
We are proposing that the OBD system on engines equipped with any
form of secondary air delivery system be required to monitor the proper
functioning of the secondary air delivery system, including all air
switching valve(s). The individual electronic components (e.g.,
actuators, valves, sensors) in the secondary air system would have to
be monitored in accordance with the comprehensive component
requirements discussed in section II.D.4.
i. Secondary Air System Low Flow Malfunctions
We are proposing that the OBD system detect a secondary air system
malfunction prior to a decrease from the manufacturer's specified air
flow during normal operation that would cause an engine's emissions to
exceed the emissions thresholds for ``other monitors'' as shown in
Table II.C-1.\38\ For engines in which no deterioration or failure of
the secondary air system would result in an engine's emissions
exceeding any of the applicable emissions thresholds, the OBD system
would have to detect a malfunction when no detectable amount of air
flow is delivered during normal operation of the secondary air system.
---------------------------------------------------------------------------

\38\ For purposes of secondary air system malfunctions, ``air
flow'' is defined as the air flow delivered by the secondary air
system to the exhaust system. For engines using secondary air
systems with multiple air flow paths/distribution points, the air
flow to each bank (i.e., a group of cylinders that share a common
exhaust manifold, catalyst, and control sensor) must be monitored in
accordance with these malfunction criteria. Also, ``normal
operation'' is defined as the condition where the secondary air
system is activated during catalyst and/or engine warm-up following
engine start. ``Normal operation'' does not include the condition
where the secondary air system is intrusively turned on solely for
the purpose of monitoring.
---------------------------------------------------------------------------

ii. Secondary Air System High Flow Malfunctions
We are proposing that the OBD system detect a secondary air system
malfunction prior to an increase from the manufacturer's specified air
flow during normal operation that would cause an engine's emissions to
exceed the emissions thresholds for ``other monitors'' as shown in
Table II.C-1.\39\ For engines in which no deterioration or failure of
the secondary air system would result in an engine's emissions
exceeding any of the applicable emissions thresholds, the OBD system
would have to detect a malfunction when no detectable amount of air
flow is delivered during normal operation of the secondary air system.
---------------------------------------------------------------------------

\39\ Ibid.
---------------------------------------------------------------------------

c. Secondary Air System Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for malfunctions of the secondary air system such that the
minimum performance ratio requirements discussed in section II.E would
be met. For purposes of tracking and reporting as required in section
II.E, all monitors used to detect malfunctions of the secondary air
system during its normal operation must be tracked separately but
reported as a single set of values as specified in section II.E
d. Secondary Air System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.
6. Catalytic Converter Monitoring
a. Background
Three-way catalysts are one of the most important emission-control
components on gasoline engines. They consist of ceramic or metal
substrates coated with the one or more of the platinum group metals
(PGM) platinum, palladium, and rhodium. These PGMs are dispersed within
an alumina washcoat containing ceria, and the substrates are mounted in
a stainless steel container in the vehicle exhaust system. Three-way
catalysts are capable of oxidizing HC emissions, oxidizing CO emissions,
and reducing NO_X emissions, hence the term three-way.
While continuous improvements to catalysts have increased their
durability, their performance still deteriorates, especially when
subjected to very high temperatures. Such high temperatures can be
caused by, among other factors, engine misfire which results in
unburned fuel and air entering and igniting in the catalyst. Exposure
to such high temperatures will result in reduced catalyst conversion
efficiency. Catalyst efficiency can also deteriorate via poisoning if
exposed to lead, phosphorus, or high sulfur levels. Catalysts can also
fail by mechanical means such as excessive vibration. Given its
importance to emissions control and the many factors that can reduce
its effectiveness, the catalyst is one of the most important components
to be monitored.
b. Catalytic Converter Monitoring Requirements
We are proposing that the OBD system monitor the catalyst system
for proper conversion capability. Specifically, the OBD system would be
required to detect a catalyst system malfunction when the catalyst
system's conversion capability decreases to the point that any of the
following occurs:
? NMHC and/or NO_X emissions exceed the emissions
thresholds for the ``catalytic converter system'' as shown in Table II.C-1.
For purposes of determining the catalyst system malfunction
criteria the manufacturer would be required to use a catalyst system
deteriorated to the malfunction criteria using methods established by
the manufacturer to

[[Page 3230]]

represent real world catalyst deterioration under normal and
malfunctioning operating conditions. The malfunction criteria must be
established by using a catalyst system with all monitored and
unmonitored catalysts simultaneously deteriorated to the malfunction
criteria.\40\ For engines using fuel shutoff to prevent over-fueling
during misfire conditions (see section II.C.2), the malfunction
criteria could be established using a catalyst system with all
monitored catalysts simultaneously deteriorated to the malfunction
criteria and all unmonitored catalysts deteriorated to the end of the
engine's useful life.
---------------------------------------------------------------------------

\40\ The unmonitored portion of the catalyst system would be
that portion downstream of the sensor(s) used for catalyst monitoring.
---------------------------------------------------------------------------

c. Catalytic Converter Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for malfunctions of the catalytic converter system such that
the minimum performance ratio requirements discussed in section II.E
would be met. For purposes of tracking and reporting as required in
section II.E, all monitors used to detect malfunctions of the catalytic
converter system during its normal operation must be tracked separately
but reported as a single set of values as specified in section II.E.
d. Catalytic Converter MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2. Note that the monitoring
method for the catalyst(s) would have to be capable of detecting all
instances, except diagnostic self-clearing, when a catalyst DTC has
been cleared but the catalyst has not been replaced (e.g., catalyst
over temperature histogram approaches are not acceptable).
7. Evaporative Emission Control System Monitoring
a. Background
The evaporative emission control system controls HC emissions that
would otherwise evaporate from the vehicle's fuel tank and fuel lines.
Should any leak develop in the evaporative emission control system--
e.g., a disconnected hose--the HC emissions can be quite high and well
over the evaporative emissions standards. Additionally, evaporative
purge system defects--e.g., deteriorated vacuum lines, damaged
canisters, non-functioning purge control valves--may occur which could
also result in very high evaporative emissions.
b. Evaporative System Monitoring Requirements
We are proposing that the OBD system verify purge flow from the
evaporative system and detect any vapor leaks from the complete
evaporative system, excluding the tubing and connections between the
purge valve and the intake manifold. Individual components of the
evaporative system (e.g. valves, sensors) must be monitored in
accordance with the comprehensive components requirements discussed in
section II.D.4.
The OBD system would be required to detect an evaporative system
malfunction when any of the following conditions exist:
? No purge flow from the evaporative system to the engine can be
detected by the OBD system (i.e., the ``purge flow'' requirement); or
? For the 2010 and later model years, the complete
evaporative system contains a leak or leaks that cumulatively are
greater than or equal to a leak caused by a 0.150 inch diameter orifice
(i.e., the ``system leak'' requirement).\41\
---------------------------------------------------------------------------

\41\ In their HDOBD regulation, 13 CCR 1971.1, CARB defines
``orifice'' as an O'Keefe Controls Co. precision metal ``Type B''
orifice with NPT connections with a diameter of the specified
dimension (e.g., part number B-31-SS for a stainless steel 0.031
inch diameter orifice).
---------------------------------------------------------------------------

If the most reliable monitoring method available cannot reliably
detect a system leak as specified above, a manufacturer may design
their system to detect a larger leak. The manufacturer would be
required to provide data and/or engineering analyses that demonstrate
the inability of the monitor to reliably detect the required leak and
their justification for detecting at their proposed orifice size.
Further, if the manufacturer can demonstrate that leaks of the required
size cannot cause evaporative or running loss emissions to exceed 1.5
times the applicable evaporative emissions standards, the Administrator
would revise upward the required leak size to the size demonstrated by
the manufacturer that would result in emissions exceeding 1.5 times the
standards.
c. Evaporative System Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for both purge flow and system leak malfunctions such that
the minimum performance ratio requirements discussed in section II.E
would be met. For purposes of tracking and reporting as required in
section II.E, all monitors used to detect system leak malfunctions must
be tracked separately but reported as a single set of values as
specified in section II.E.
Manufacturers may disable or abort an evaporative emission control
system monitor when the fuel tank level is over 85 percent of nominal
tank capacity or during a refueling event. Manufacturers may design
their evaporative emission control system monitor such that it executes
only during drive cycles determined by the manufacturer to be cold
starts if such a condition is needed to ensure reliable monitoring. The
manufacturer would have to provide data and/or an engineering
evaluation demonstrating that a reliable check can only be made on
drive cycles when the cold start criteria are satisfied. However, the
manufacturer may not determine a cold start solely on the basis that
ambient temperature is higher than engine coolant temperature at engine
start. Lastly, manufacturers would be allowed to disable temporarily
the evaporative purge system to perform an evaporative system leak check.
d. Evaporative System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2, with an exception for leaks
associated with the fuel filler cap. If the OBD system is capable of
discerning that a system leak is being caused by a missing or
improperly secured fuel filler cap, the manufacturer is not required to
illuminate the MIL or store a DTC provided the vehicle is equipped with
an alternative indicator for notifying the vehicle operator of the fuel
filler cap ``malfunction.'' The alternative indicator would have to be
of sufficient illumination and location to be readily visible to the
vehicle operator under all lighting conditions. However, if the vehicle
is not equipped with an alternative indicator and, instead, the MIL is
illuminated to inform the operator of the ``malfunction,'' the MIL may
be extinguished and the corresponding DTC(s) erased once the OBD system
has verified that the fuel filler cap has been securely fastened and
the MIL has not been commanded ON for any other type of malfunction.
The Administrator may approve other strategies provided the
manufacturer was able to demonstrate that the vehicle operator would be
promptly notified of the missing or improperly secured fuel filler cap
and that the notification would reasonably result in corrective action
being undertaken.

[[Page 3231]]

8. Exhaust Gas Sensor Monitoring
a. Background
Exhaust gas sensors (e.g., oxygen sensors, air-fuel ratio (A/F)
sensors) are a critical element of the emissions control system on
gasoline engines. In addition to maintaining a stoichiometric air-fuel
mixture and, thus, helping to achieve the lowest possible emissions,
these sensors are also used for enhancing the performance of several
emission control technologies--e.g., catalysts, EGR systems). Many
modern vehicles control the fuel supply with an oxygen sensor feedback
system to maintain stoichiometry. Oxygen sensors are located typically
in the exhaust system upstream and downstream of the catalytic
converters. The front, or upstream, oxygen sensor is used generally for
fuel control. The rear, or downstream, oxygen sensor is used generally
for adjusting the front oxygen sensor signal as it drifts slightly with
age related deterioration--often referred to as fuel trimming--and for
onboard monitoring the catalyst system. Many vehicles use A/F sensors
in lieu of the more conventional oxygen sensors since A/F sensors
provide a precise reading of the actual air-fuel ratio.
We expect that heavy-duty gasoline manufacturers will use both of
these types of sensors to optimize their emissions control strategies
and to satisfy many of the proposed heavy-duty OBD monitoring
requirements--fuel system monitoring, catalyst monitoring, EGR system
monitoring. Since exhaust gas sensors can be a critical component of an
engine's fuel and emissions control system, their proper performance
needs to be assured to maintain low emissions. Thus, any malfunction
that adversely affects the performance of any of these exhaust gas
sensors should be detected by the OBD system.
b. Exhaust Gas Sensor Monitoring Requirements
We are proposing that the OBD system monitor the output signal,
response rate, and any other parameter that could affect emissions of
all primary (i.e., fuel control) exhaust gas sensors for malfunction.
Both the lean to rich and rich to lean response rates must be
monitored. In addition, we are proposing that the OBD system monitor
all secondary exhaust gas sensors (i.e., those used for fuel trimming
or as a monitoring device for another system) for proper output signal,
activity, and response rate. For engines equipped with heated exhaust
gas sensors, the OBD system would be required to monitor the sensor
heater for proper performance.
i. Primary Exhaust Gas Sensors
We are proposing that the OBD system detect a malfunction prior to
any failure or deterioration of the exhaust gas sensor output voltage,
resistance, impedance, current, response rate, amplitude, offset, or
other characteristic(s) (including drift or bias corrected for by
secondary sensors) that would cause an engine's emissions to exceed the
emissions thresholds for ``other monitors'' as shown in Table II.C-1.
The OBD system would also be required to detect the following exhaust
gas sensor malfunctions:
? Those caused by either a lack of circuit continuity or
out-of-range values.
? Those where a sensor failure or deterioration causes the
fuel system to stop using that sensor as a feedback input (e.g., causes
default or open-loop operation).
? Those where the sensor output voltage, resistance,
impedance, current, amplitude, activity, or other characteristics are
no longer sufficient for use as an OBD system monitoring device (e.g.,
for catalyst monitoring).
ii. Secondary Exhaust Gas Sensors
We are proposing that the OBD system detect a malfunction prior to
any failure or deterioration of the exhaust gas sensor voltage,
resistance, impedance, current, response rate, amplitude, offset, or
other characteristic(s) that would cause an engine's emissions to
exceed the emissions thresholds for ``other monitors'' as shown in
Table II.C-1. The OBD system would also be required to detect the
following exhaust gas sensor malfunctions:
? Those caused by either a lack of circuit continuity or
out-of-range values.
? Those where a sensor failure or deterioration causes the
fuel system to stop using that sensor as a feedback input (e.g., causes
default or open-loop operation).
? Those where the sensor output voltage, resistance,
impedance, current, amplitude, activity, or other characteristics are
no longer sufficient for use as an OBD system monitoring device (e.g.,
for catalyst monitoring).
iii. Exhaust Gas Sensor Heaters
We are proposing that the OBD system detect a malfunction of the
sensor heater performance when the current or voltage drop in the
heater circuit is no longer within the manufacturer's specified limits
for normal operation (i.e., within the criteria required by the
component vendor for heater circuit performance at high mileage). The
manufacturer may use other malfunction criteria for heater performance
malfunctions. To do so, the manufacturer would be required to submit
data and/or engineering analyses that demonstrate that the monitoring
reliability and timeliness would be equivalent to the criteria stated here.
In addition, the OBD system would be required to detect
malfunctions of the heater circuit including open or short circuits
that conflict with the commanded state of the heater (e.g., shorted to
12 Volts when commanded to 0 Volts (ground)).
c. Exhaust Gas Sensor Monitoring Conditions
i. Primary Exhaust Gas Sensors
We are proposing that manufacturers define the monitoring
conditions for primary exhaust gas sensor malfunctions causing
exceedance of the applicable thresholds and/or inability to perform as
an OBD monitoring device such that the minimum performance ratio
requirements discussed in section II.E would be met. For purposes of
tracking and reporting as required in section II.E, all such monitors
must be tracked separately but reported as a single set of values as
specified in section II.E.
Monitoring for primary exhaust gas sensor malfunctions related to
circuit continuity, out-of-range, and open-loop operation must be done
continuously with the exception that manufacturers may disable
continuous exhaust gas sensor monitoring when an exhaust gas sensor
malfunction cannot be distinguished from other effects. As an example,
a manufacturer may disable monitoring for out-of-range on the low side
during conditions where fuel has been cut (i.e., shut off temporarily).
To do so, the manufacturer would have to submit data and/or engineering
analyses that demonstrate that a properly functioning sensor cannot be
distinguished from a malfunctioning sensor and that the disablement
interval is limited only to that necessary for avoiding a false detection.
ii. Secondary Exhaust Gas Sensors
We are proposing that manufacturers define the monitoring
conditions for secondary exhaust gas sensor malfunctions causing
exceedance of the applicable emissions thresholds, lack of circuit
continuity, and/or inability to perform as an OBD monitoring device
such that the minimum performance ratio requirements discussed in
section II.E would be met.
Monitoring for secondary exhaust gas sensor malfunctions related to
out-of-

[[Page 3232]]

range and open loop operation must be done continuously with the
exception that manufacturers may disable continuous exhaust gas sensor
monitoring when an exhaust gas sensor malfunction cannot be
distinguished from other effects. As an example, a manufacturer may
disable monitoring for out-of-range on the low side during conditions
where fuel has been cut (i.e., shut off temporarily). To do so, the
manufacturer would have to submit data and/or engineering analyses that
demonstrate that a properly functioning sensor cannot be distinguished
from a malfunctioning sensor and that the disablement interval is
limited only to that necessary for avoiding a false detection.
iii. Sensor Heaters
We are proposing that manufacturers define monitoring conditions
for sensor heater performance malfunctions such that the minimum
performance ratio requirements discussed in section II.E would be met.
Monitoring for sensor heater circuit malfunctions must be done continuously.
d. Exhaust Gas Sensor MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.

D. Monitoring Requirements and Timelines for Other Diesel and Gasoline
Systems

1. Variable Valve Timing and/or Control (VVT) System Monitoring
a. Background
Variable valve timing (VVT) and/or control systems are used
primarily to optimize engine performance and have many advantages over
conventional valve control. Instead of opening and closing the valves
by fixed amounts and at fixed times, VVT controls can vary the timing
of valve opening/closing and vary the effective size of the valve
opening itself (in some systems) depending on the driving conditions
(e.g., high engine speed and load). This feature permits a better
compromise between performance, driveability, and emissions than
conventional systems. With more stringent NO_X emission
standards being phased in, more vehicles are anticipated to use VVT. By
doing so, some exhaust gas can be retained in the combustion chamber
thereby reducing peak combustion temperatures and, hence,
NO_X emissions (known as ``internal EGR'').
b. VVT and/or Control System Monitoring Requirements
We are proposing that the OBD system monitor the VVT system on
engines so equipped for target error and slow response malfunctions.
The individual electronic components (e.g., actuators, valves, sensors)
that are used in the VVT system must be monitored in accordance with
the comprehensive components requirements in section II.D.4.
i. VVT Target Error Malfunctions
We are proposing that the OBD system detect a malfunction prior to
any failure or deterioration in the capability of the VVT system to
achieve the commanded valve timing and/or control within a crank angle
and/or lift tolerance that would cause an engine's emissions to exceed
the emissions thresholds for ``other monitors'' as shown in Table II.B-
1 for diesel engines or Table II.C-1 for gasoline engines. For engines
in which no failure or deterioration of the VVT system could result in
an engine's emissions exceeding the applicable emissions thresholds,
the OBD system would have to detect a malfunction of the VVT system
when proper functional response of the system to computer commands does
not occur.
ii. VVT Slow Response Malfunctions
We are proposing that the OBD system detect a malfunction prior to
any failure or deterioration in the capability of the VVT system to
achieve the commanded valve timing and/or control within a
manufacturer-specified time that would cause an engine's emissions to
exceed the emissions thresholds for ``other monitors'' as shown in
Table II.B-1 for diesel engines or Table II.C-1 for gasoline engines.
For engines in which no failure or deterioration of the VVT system
could result in an engine's emissions exceeding the applicable
emissions thresholds, the OBD system would have to detect a malfunction
of the VVT system when proper functional response of the system to
computer commands does not occur.
c. VVT and/or Control System Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for VVT target error or slow response malfunctions such that
the minimum performance ratio requirements discussed in section II.E
would be met with the exception that monitoring shall occur every time
the monitoring conditions are met during the driving cycle rather than
once per driving cycle as required for most monitors. For purposes of
tracking and reporting as required in section II.E, all monitors used
to detect all VVT related malfunctions would have to be tracked
separately but reported as a single set of values as specified in
section II.E.\42\
---------------------------------------------------------------------------

\42\ For specific components or systems that have multiple
monitors that are required to be reported (e.g., exhaust gas sensor
bank 1 may have multiple monitors for sensor response or other
sensor characteristics), the OBD system must separately track
numerators and denominators for each of the specific monitors and
report only the corresponding numerator and denominator for the
specific monitor that has the lowest numerical ratio. If two or more
specific monitors have identical ratios, the corresponding numerator
and denominator for the specific monitor that has the highest
denominator shall be reported for the specific component.
---------------------------------------------------------------------------

d. VVT and/or Control System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.
2. Engine Cooling System Monitoring
a. Background
We are concerned about two elements of the engine cooling system.
These elements are the thermostat and the engine coolant temperature
sensor. Manufacturers typically use a thermostat to control the flow of
coolant through the radiator and around the engine. During a cold
engine start, the thermostat is closed typically which prevents the
flow of coolant and serves to promote more rapid warm-up of the engine.
As the coolant approaches a specific temperature, the thermostat begins
to open allowing circulation of coolant through the radiator and around
the engine. The thermostat then acts to regulate the coolant to the
specified temperature. If the temperature rises above the regulated
temperature, the thermostat opens further to allow more coolant to
circulate, thus reducing the temperature. If the temperature drops
below the regulated temperature, the thermostat partially closes to
reduce the amount of coolant circulating, thereby increasing the
temperature. If a thermostat malfunctions in such a manner that it does
not adequately restrict coolant flow during vehicle warm-up, an
increase in emissions could occur due to prolonged operation of the
vehicle at temperatures below the stabilized, warmed-up value. This is
particularly true at lower ambient temperatures--50 degrees Fahrenheit
and below--but not so low that they are rare in the U.S. Equally
important is that the engine coolant temperature is often used as an
enable criterion for many OBD monitors. If the engine's coolant
temperature does not reach the

[[Page 3233]]

manufacturer-specified warmed-up value, such monitors would be
effectively disabled, perhaps indefinitely, and would, therefore, never
detect malfunctions.
Closely linked with the thermostat is the engine coolant
temperature (ECT) sensor. Manufacturers typically use an ECT sensor as
an input for many of the emission-related engine control systems. For
gasoline engines, the ECT sensor is often one of the most important
factors in determining when to begin closed-loop fuel control. If the
engine coolant does not warm-up sufficiently, closed-loop fuel control
is usually not engaged and the vehicle remains in open-loop fuel
control. Since open-loop fuel control does not provide the precision of
closed-loop control, the result is increased emissions levels. For
diesel engines, the ECT sensor is often used to engage closed-loop
control of the EGR system. Similar to closed-loop fuel control on
gasoline engines, if the coolant temperature does not warm up, closed-
loop control of the EGR system would not engage which would result in
increased emissions levels. In addition, for both gasoline and diesel
engines, the ECT sensor may be used to enable many of the monitors that are
being proposed. Such monitors would be effectively disabled and incapable
of detecting malfunctions should the ECT sensor itself malfunction.
b. Engine Cooling System Monitoring Requirements
We are proposing that the OBD system monitor the thermostat on
engines so equipped for proper operation. We are also proposing that
the OBD system monitor the ECT sensor for circuit continuity, out-of-
range values, and rationality faults. For engines that use an approach
other than the cooling system and ECT sensor--e.g., oil temperature,
cylinder head temperature--for an indication of engine operating
temperature for emission control purposes (e.g., to modify spark or
fuel injection timing or quantity), the manufacturer may forego cooling
system monitoring in favor of monitoring the components or systems used
in their approach. To do so, the manufacturer would be required to
submit data and/or engineering analyses that demonstrate that their
monitoring plan is as reliable and effective as the monitoring required
for the engine cooling system.
i. Thermostat Monitoring Requirements
We are proposing that the OBD system detect a thermostat
malfunction if, within the manufacturer specified time interval
following engine start, any of the following conditions occur:
? The coolant temperature does not reach the highest
temperature required by the OBD system to enable other diagnostics;
? The coolant temperature does not reach a warmed-up
temperature within 20 degrees Fahrenheit of the manufacturer's nominal
thermostat regulating temperature. The manufacturer may use a lower
temperature for this criterion provided the manufacturer can
demonstrate that the fuel, spark timing, and/or other coolant
temperature-based modification to the engine control strategies would
not cause an emissions increase greater than or equal to 50 percent of
any of the applicable emissions standards.
The time interval specified by the manufacturer would have to be
supported by the manufacturer via data and/or engineering analyses
demonstrating that it provides robust monitoring and minimizes the
likelihood of other OBD monitors being disabled. The manufacturer may
use alternative malfunction criteria that are a function of temperature
at engine start on engines that do not reach the temperatures specified
in the malfunction criteria when the thermostat is functioning
properly. To do so, the manufacturer would be required to submit data
and/or engineering analyses that demonstrate that a properly operating
system does not reach the specified temperatures and that the
possibility is minimized for cooling system malfunctions to go
undetected and disable other OBD monitors. In some cases, a
manufacturer may forgo thermostat monitoring if the manufacturer can
demonstrate that a malfunctioning thermostat cannot cause a measurable
increase in emissions during any reasonable driving condition nor cause
any disablement of other OBD monitors.
ii. Engine Coolant Temperature Sensor Monitoring Requirements
We are proposing that the OBD system detect an ECT sensor
malfunction when a lack of circuit continuity or an out-of-range value
occurs. We are also proposing that the OBD system detect if, within the
manufacturer specified time interval following engine start, the ECT
sensor does not achieve the highest stabilized minimum temperature that
is needed to initiate closed-loop/feedback control of all affected
emission control systems (e.g., fuel system, EGR system). The
manufacturer specified time interval would have to be a function of the
engine coolant temperature and/or intake air temperature at startup.
The manufacturer time interval would also have to be supported by the
manufacturer via data and/or engineering analyses demonstrating that it
provides robust monitoring and minimizes the likelihood of other OBD
monitors being disabled. Manufacturers may forego the requirement to
detect the ``time to closed loop/feedback enable temperature''
malfunction if the manufacturer does not use engine coolant temperature
or the ECT sensor to enable closed-loop/feedback control of any
emission control systems.
We are also proposing that, to the extent feasible when using all
available information, the OBD system must detect a malfunction if the
ECT sensor inappropriately indicates a temperature below the highest
minimum enable temperature required by the OBD system to enable other
monitors. For example, an OBD system that requires an engine coolant
temperature greater than 140 degrees Fahrenheit prior to enabling an
OBD monitor must detect malfunctions that cause the ECT sensor to
indicate inappropriately a temperature below 140 degrees Fahrenheit.
Manufacturers may forego such monitoring within temperature regions in
which the thermostat monitor or the ECT sensor ``time to reach closed-
loop/feedback enable temperature'' monitor would detect this ``stuck in
a range below the highest minimum enable temperature'' ECT sensor
malfunction.
Lastly, we are proposing that, to the extent feasible when using
all available information, the OBD system must detect a malfunction if
the ECT sensor inappropriately indicates a temperature above the lowest
maximum enable temperature required by the OBD system to enable other
monitors. For example, an OBD system that requires an engine coolant
temperature less than 90 degrees Fahrenheit at startup prior to
enabling an OBD monitor must detect malfunctions that cause the ECT
sensor to indicate inappropriately a temperature above 90 degrees
Fahrenheit. Manufacturers may forego such monitoring within temperature
regions in which the thermostat monitor, the ECT sensor ``time to reach
closed-loop/feedback enable temperature'' monitor, or the ECT sensor
``stuck in a range below the highest minimum enable temperature''
monitor would detect this ECT sensor ``stuck in a range above the
lowest maximum enable temperature'' ECT sensor malfunction. The
manufacturer may also forego such monitoring if the MIL would be
illuminated for entering a ``limp home'' or default mode of

[[Page 3234]]

operation--e.g., for an over temperature protection strategy--as
discussed in section II.A.2. Manufacturers may also forego this
monitoring within temperature regions where the temperature gauge
indicates a temperature in the engine overheating ``red zone'' should
the vehicle have a temperature gauge on the instrument panel that
displays the same temperature information as used by the OBD system
(note that a temperature gauge would be required, not a temperature
warning light).
c. Engine Cooling System Monitoring Conditions
i. Thermostat Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for thermostat malfunctions in accordance with the general
monitoring conditions for all engines described in section II.A.3.
Additionally, monitoring for thermostat malfunctions would have to be
done once per drive cycle on every drive cycle in which the ECT sensor
indicates, at engine start, a temperature lower than the temperature
established as the malfunction criteria in section II.D.2.b.i.
Manufacturers would be allowed to disable thermostat monitoring at
ambient engine start temperatures below 20 degrees Fahrenheit.
Manufacturers may suspend or disable thermostat monitoring if the
engine is subjected to conditions that could lead to false diagnosis
(e.g., engine operation at idle for more than 50 percent of the warm-up
time and/or hot restart conditions). To do so, the manufacturer must
submit data and/or engineering analyses that demonstrate that the
suspension or disablement is necessary. In general, the manufacturer
would not be allowed to suspend or disable the thermostat monitor on
engine starts where the engine coolant temperature at engine start is
more than 35 degrees Fahrenheit lower than the thermostat malfunction
threshold temperature.
ii. Engine Coolant Temperature Sensor Monitoring Conditions
We are proposing that monitoring for ECT sensor circuit continuity
and out-of-range malfunctions be done continuously. Manufacturers would
be allowed to disable continuous ECT sensor monitoring when an ECT
sensor malfunction cannot be distinguished from other effects. To do
so, the manufacturer would have to submit test data and/or engineering
evaluation that demonstrate that a properly functioning sensor cannot
be distinguished from a malfunctioning sensor and that the disablement
interval is limited only to that necessary for avoiding false detection.
We are also proposing that manufacturers define the monitoring
conditions for ``time to reach closed-loop/feedback enable
temperature'' malfunctions in accordance with the general monitoring
conditions for all engines described in section II.A.3. Additionally,
monitoring for ``time to reach closed-loop/feedback enable
temperature'' malfunctions would have to be conducted once per drive
cycle on every drive cycle in which the ECT sensor at engine start
indicates a temperature lower than the closed-loop enable temperature
(i.e., all engine start temperatures greater than the ECT sensor out-
of-range low temperature and less than the closed-loop enable
temperature). Manufacturers would be allowed to suspend or delay the
``time to reach closed-loop/feedback enable temperature'' monitor if
the engine is subjected to conditions that could lead to false
diagnosis (e.g., vehicle operation at idle for more than 50 to 75
percent of the warm-up time).
We are also proposing that manufacturers define the monitoring
conditions for ECT sensor ``stuck in a range below the highest minimum
enable temperature'' and ``stuck in a range above the lowest maximum
enable temperature'' malfunctions in accordance with the general
monitoring conditions for all engines described in section II.A.3 and
in accordance with the minimum performance ratio requirements discussed
in section II.E.
d. Engine Cooling System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2.
3. Crankcase Ventilation System Monitoring
a. Background
Crankcase emissions are the pollutants emitted in the gases that
are vented from an engine's crankcase. These gases are also referred to
as ``blowby gases'' because they result from engine exhaust from the
combustion chamber ``blowing by'' the piston rings into the crankcase.
These gases are vented to prevent high pressures from occurring in the
crankcase. Our emission standards have historically prohibited
crankcase emissions from all highway engines except turbocharged heavy-
duty diesel engines. The most common way to eliminate crankcase
emissions has been to vent the blowby gases into the engine air intake
system, so that the gases can be recombusted. We made the exception for
turbocharged heavy-duty diesel engines in the past because of concerns
about fouling that could occur by routing the diesel particulates
(including engine oil) into the turbocharger and aftercooler. Newly
developed closed crankcase filtration systems specifically designed for
turbocharged heavy-duty diesel engines now allow the crankcase gases to
be captured.
In general, the crankcase ventilation system consists of a fresh
air inlet hose, a crankcase vapor outlet hose, and a crankcase
ventilation valve to control the flow through the system. Fresh air is
introduced to the crankcase via the inlet (typically a connection from
the intake air cleaner assembly). On the opposite side of the
crankcase, vapors are vented from the crankcase through the valve by
way of the outlet hose and then to the intake manifold. On gasoline
engines, the intake manifold provides the vacuum that is needed to
accomplish the circulation while the engine is running.
For gasoline engines, the valve is used to regulate the amount of
flow based on engine speed. During low engine load operation (e.g.,
idle), the valve is nearly closed allowing only a small portion of air
to flow through the system. With open throttle conditions, the valve
opens to allow more air into the system. At high engine load operation
(i.e., hard accelerations), the valve begins to close again, limiting
air flow to a small amount. For most systems, a mechanical valve is all
that is necessary to adequately regulate crankcase ventilation system
air flow. The crankcase ventilation system on diesel engines, while
slightly different than that for gasoline engines, has essentially the
same purpose and function.
We do not believe that failures involving cracked or deteriorated
hoses have a significant impact on crankcase emissions because vapors
are drawn into the engine by intake manifold vacuum which suggests that
fresh air would be drawn into the cracked hose rather than dirty
exhaust being blown out of the cracked hose. The more likely cause of
crankcase ventilation system malfunctions and excess emissions is
improper service or tampering of the system. Such failures include
misrouted or disconnected hoses and missing valves. Of these failures,
hose disconnections on the vapor vent side of the system and/or missing
valves can cause harmful crankcase emissions to be vented directly to
the atmosphere.

[[Page 3235]]

b. Crankcase Ventilation System Monitoring Requirements
We are proposing that the OBD system monitor the crankcase
ventilation system on engines so equipped for system integrity. Engines
not equipped with crankcase ventilation systems would be exempt from
monitoring the crankcase ventilation system.
Specifically for diesel engines, the manufacturer would be required
to submit a plan for the monitoring strategy, malfunction criteria, and
monitoring conditions prior to OBD certification. The plan would have
to demonstrate the effectiveness of the strategy to monitor the
performance of the crankcase ventilation system to the extent feasible
with respect to the malfunction criteria below and the monitoring
conditions required by the monitor.
We are proposing that the OBD system detect a malfunction of the
crankcase ventilation system when a disconnection of the system occurs
between either the crankcase and the crankcase ventilation valve, or
between the crankcase ventilation valve and the intake manifold.
Manufacturers may forego detecting a disconnection between the
crankcase and the crankcase ventilation valve provided the manufacturer
can demonstrate that the crankcase ventilation system is designed such
that the crankcase ventilation valve is fastened directly to the
crankcase in a manner that makes it significantly more difficult to
remove the valve from the crankcase than to disconnect the line between
the valve and the intake manifold (aging effects must be taken into
consideration). Manufacturers may also forego detecting a disconnection
between the crankcase and the crankcase ventilation valve for system
designs that use tubing between the valve and the crankcase provided
the manufacturer can demonstrate that the connections between the valve
and the crankcase are: (1) Resistant to deterioration or accidental
disconnection; (2) significantly more difficult to disconnect than the
line between the valve and the intake manifold; and, (3) not subject to
disconnection per the manufacturer's repair procedures for non-
crankcase ventilation system repair work. Lastly, manufacturers may
forego detecting a disconnection between the crankcase ventilation
valve and the intake manifold upon determining that the disconnection:
(1) Causes the vehicle to stall immediately during idle operation; or,
(2) is unlikely to occur due to a crankcase ventilation system design
that is integral to the induction system (e.g., machined passages
rather than tubing or hoses).
c. Crankcase Ventilation System Monitoring Conditions
We are proposing that manufacturers define the monitoring
conditions for crankcase ventilation system malfunctions in accordance
with the general monitoring conditions for all engines described in
section II.A.3, and the minimum performance ratio requirements
discussed in section II.E.
d. Crankcase Ventilation System MIL Illumination and DTC Storage
We are proposing the general requirements for MIL illumination and
DTC storage as discussed in section II.A.2. The stored DTC need not
specifically identify the crankcase ventilation system (e.g., a DTC for
idle speed control or fuel system monitoring can be stored) if the
manufacturer can demonstrate that additional monitoring hardware would
be necessary to make this identification, and provided the
manufacturer's diagnostic and repair procedures for the detected
malfunction include directions to check the integrity of the crankcase
ventilation system.
4. Comprehensive Component Monitors
a. Background
Comprehensive components is a term meant to capture essentially
every other emissions related component not discussed above.
Specifically, it covers all other electronic engine components or
systems not mentioned above that either can affect vehicle emissions or
are used as part of the OBD diagnostic strategy for another monitored
component or system. Comprehensive components are generally identified
as input components--i.e., those that provide input directly or
indirectly to the onboard computer--or as output components and/or
systems--i.e., those that receive commands from the onboard computer.
Typical examples of input components include temperature sensors and
pressure sensors, while examples of output components and/or systems
include the idle control system, glow plugs, and wait-to-start lamps.
While a malfunctioning comprehensive component may not have as much
impact on emissions as a malfunctioning major emissions-related
component, it still could result in a measurable increase in emissions.
The proper performance of these components can be critical to both the
proper functioning of major emissions-related components, and to the
accurate monitoring of those components or systems. Malfunctions of
comprehensive components that go undetected by the OBD system may
disable or adversely affect the robustness of other OBD monitors
without any awareness by the operator that a problem exists. Due to the
vital role these components play, monitoring them properly is extremely
important.
b. Comprehensive Component Monitoring Requirements
We are proposing that the OBD system monitor for malfunction any
electronic engine components/systems not otherwise described in
sections above that either provides input to (directly or indirectly)
or receives commands from the onboard computer(s), and: (1) Can affect
emissions during any reasonable in-use driving condition; or, (2) is
used as part of the diagnostic strategy for any other monitored system
or component.\43\
---------------------------------------------------------------------------

\43\ When referring to ``comprehensive components'' and their
monitors, ``electronic engine components/systems'' is not meant to
include components/systems that are driven by the engine yet are not
related to the control of the fueling, air handling, or emissions of
the engine (e.g., PTO components, air conditioning system
components, and power steering components are not included).
---------------------------------------------------------------------------

Input components required to be monitored may include the crank
angle sensor, knock sensor, throttle position sensor, cam position
sensor, intake air temperature sensor, boost pressure sensor, manifold
pressure sensor, mass air flow sensor, exhaust temperature sensor,
exhaust pressure sensor, fuel pressure sensor, and fuel composition
sensor (e.g., flexible fuel vehicles). Output components/systems
required to be monitored may include the idle speed control system,
glow plug system, variable length intake manifold runner systems,
supercharger or turbocharger electronic components, heated fuel
preparation systems, the wait-to-start lamp on diesel applications, and
the MIL. The manufacturer would be responsible for determining which
input and output components/systems could affect emissions during any
reasonable in-use driving condition. The manufacturer would be allowed
to make this determination based on data or engineering judgment.
However, if the Administrator reasonably believes that a manufacturer
has incorrectly determined that a component/system cannot affect
emissions, the manufacturer may be required to provide emissions data
showing that the component/system, when malfunctioning and installed in
a suitable test engine, does not have an emissions effect. Such
emissions data may be requested for any reasonable driving condition.

[[Page 3236]]

i. Input Components
We are proposing that the OBD system detect malfunctions of input
components caused by a lack of circuit continuity, out-of-range values,
and, where feasible, improper rationality. To the extent feasible, the
rationality diagnostics should verify that a sensor's input to the
onboard computer is neither inappropriately high nor inappropriately
low (i.e., ``two-sided'' diagnostics should be used). Also to the
extent feasible, the OBD system should detect and store different DTCs
that distinguish rationality malfunctions from lack of circuit
continuity malfunctions and out-of-range values. For lack of circuit
continuity malfunctions and out-of-range values, the OBD system should
detect and store different DTCs for each distinct malfunction (e.g.,
out-of-range low, out-of-range high, open circuit). The OBD system is
not required to store separate DTCs for lack of circuit continuity
malfunctions that cannot be distinguished from malfunctions associated
with out-of-range values.
For input components that are used to activate alternative
strategies that can affect emissions (e.g., AECDs, engine shutdown
systems), the OBD system would be required to detect rationality
malfunctions that cause the system to erroneously activate or
deactivate the alternative strategy. To the extent feasible when using
all available information, the rationality diagnostics should detect a
malfunction if the input component inappropriately indicates a value
that activates or deactivates the alternative strategy. For example, if
an alternative strategy requires an intake air temperature greater than
120 degrees Fahrenheit prior to activating, the OBD system should
detect malfunctions that cause the intake air temperature sensor to
inappropriately indicate a temperature above 120 degrees Fahrenheit.
For engines that require precise alignment between the camshaft and
the crankshaft, the OBD system would be required to monitor the
crankshaft position sensor(s) and camshaft position sensor(s) to verify
proper alignment between the camshaft and crankshaft. The OBD system
would also have to monitor the sensors for circuit continuity and
rationality malfunctions. Such monitoring for proper alignment between
a camshaft and a crankshaft would only be required in cases where both
are equipped with position sensors.
For engines equipped with VVT systems and a timing belt or chain,
the OBD system must detect a malfunction if the alignment between the
camshaft and crankshaft is off by one or more cam/crank sprocket cogs
(e.g., the timing belt/chain has slipped by one or more teeth/cogs). If
a manufacturer demonstrates that a single tooth/cog misalignment cannot
cause a measurable increase in emissions during any reasonable driving
condition, the OBD system would be required to detect a malfunction
when the minimum number of teeth/cogs misalignment needed to cause a
measurable emission increase has occurred.
ii. Output Components/Systems
We are proposing that the OBD system detect a malfunction of an
output component/system when proper functional response of the
component/system to computer commands does not occur. If a functional
check is not feasible, the OBD system would be required to detect
malfunctions caused by a lack of circuit continuity (e.g., short to
ground or high voltage). For output component malfunctions associated
with the lack of circuit continuity, the OBD system is not required to
store different DTCs for each distinct malfunction (e.g., open circuit,
shorted low). Further, manufacturers would not be required to activate
an output component/system when it would not normally be active for the
exclusive purpose of performing functional monitoring of output
components/systems.
Additionally, the idle control system would have to be monitored
for proper functional response to computer commands. For gasoline
engines that use monitoring strategies based on deviation from target
idle speed, a malfunction would have to be detected when either of the
following conditions occur: (a) The idle speed control system cannot
achieve the target idle speed within 200 revolutions per minute (rpm)
above the target speed or 100 rpm below the target speed--the OBD
system could use larger engine speed tolerances provided the
manufacturer is able to demonstrate via data and/or engineering
analyses that the tolerances can be exceeded without a malfunction
being present; or, (b) the idle speed control system cannot achieve the
target idle speed within the smallest engine speed tolerance range
required by the OBD system to enable any other OBD monitors. For diesel
engines, a malfunction would have to be detected when either of the
following conditions occur: (a) The idle fuel control system cannot
achieve the target idle speed or fuel injection quantity within +/-50
percent of the manufacturer-specified fuel quantity and engine speed
tolerances; or, (b) the idle fuel control system cannot achieve the
target idle speed or fueling quantity within the smallest engine speed
or fueling quantity tolerance range required by the OBD system to
enable any other OBD monitors.
Glow plugs and intake air heater systems would also have to be
monitored for proper functional response to computer commands and for
malfunctions associated with circuit continuity. The glow plug and
intake air heater circuit(s) would have to be monitored for proper
current and voltage drop. The manufacturer may use other monitoring
strategies by submitting data and/or engineering analyses that
demonstrate that the strategy provides equally reliable and timely
detection of malfunctions. In general, the OBD system would have to
detect a malfunction when a single glow plug no longer operates within
the manufacturer's specified limits for normal operation. If a
manufacturer demonstrates that a single glow plug malfunction cannot
cause a measurable increase in emissions during any reasonable driving
condition, the OBD system must detect a malfunction for the minimum
number of glow plugs needed to cause an emissions increase. Further, to
the extent feasible without adding additional hardware for this purpose,
the stored DTC must identify the specific malfunctioning glow plug(s).
Lastly, the wait-to-start lamp circuit and the MIL circuit would
have to be monitored for malfunctions that cause either lamp to fail to
illuminate when commanded on (e.g., burned out bulb).
c. Comprehensive Component Monitoring Conditions
i. Input Components
We are proposing that input components be monitored continuously
for circuit continuity and for providing values within the proper
range. For rationality monitoring, where applicable, manufacturers
would define the monitoring conditions for detecting malfunctions in
accordance with the general monitoring conditions for all engines
described in section II.A.3 and the minimum performance ratio
requirements described in section II.E except that rationality
monitoring would have to occur every time the monitoring conditions are
met during the drive cycle rather than once per drive cycle as required
in section II.A.3.
A manufacturer may disable continuous monitoring for circuit
continuity, and for providing values within the proper range, when a

[[Page 3237]]

malfunction cannot be distinguished from other effects. To do so, the
manufacturer would have to submit data and/or engineering analyses that
demonstrate that a properly functioning input component cannot be
distinguished from a malfunctioning input component and that the
disablement interval is limited only to that necessary for avoiding
false detection.
ii. Output Components/Systems
We are proposing that output components/systems be monitored
continuously for circuit continuity. For functional monitoring,
manufacturers would define the monitoring conditions for detecting
malfunctions in accordance with the general monitoring conditions for
all engines described in section II.A.3 and the minimum performance
ratio requirements described in section II.E.
For the idle control system, we are proposing that manufacturers
define the monitoring conditions for functional monitoring in
accordance with the general monitoring conditions for all engines
described in section II.A.3 and the minimum performance ratio
requirements described in section II.E except that functional
monitoring would have to occur every time the monitoring conditions are
met during the drive cycle rather than once per drive cycle as required
in section II.A.3.
A manufacturer may disable continuous monitoring for circuit
continuity when a malfunction cannot be distinguished from other
effects. To do so, the manufacturer would have to submit data and/or
engineering analyses that demonstrate that a properly functioning
output component cannot be distinguished from a malfunctioning output
component and that the disablement interval is limited only to that
necessary for avoiding false detection.
d. Comprehensive Component MIL Illumination and DTC Storage
With a couple of exceptions, we are proposing the general
requirements for MIL illumination and DTC storage as discussed in
section II.A.2. The exceptions to this being that MIL illumination
would not be required in conjunction with storing a MIL-on DTC for any
comprehensive component if: (a) The component or system, when
malfunctioning, could not cause engine emissions to increase by 15
percent or more of the FTP standard during any reasonable driving
condition; and, (b) the component or system is not used as part of the
diagnostic strategy for any other monitored system or component. MIL
illumination is also not required if a malfunction has been detected in
the MIL circuit that prevents the MIL from illuminating (e.g., burned
out bulb or light emitting diode (LED)). However, the electronic MIL
status must be reported as ``commanded on'' and a MIL-on DTC would have
to be stored.
5. Other Emissions Control System Monitoring
a. Background
As noted above, the primary purpose of OBD is to detect
malfunctions in the engine and/or emissions control system. Therefore,
we are proposing that manufacturers be required to submit to the
Administrator a monitoring plan for any new engine and/or emissions
control technology not otherwise described above. Such technology might
include hydrocarbon traps or homogeneous charge compression ignition
(HCCI) systems. This would allow manufacturers and EPA to evaluate the
new technology and determine an appropriate level of monitoring that
would be both technologically feasible and consistent with the monitoring
requirements for the other emissions control devices described above.
As proposed, the Administrator would provide guidance as to what
type of components would fall under the ``other emissions control
system'' requirements and which would fall under the comprehensive
component requirements. Specifically, we are concerned that uncertainty
may arise for those emission control components or systems that also
meet the definition of electronic engine components. As such, the
proposal would delineate the two by requiring components/systems that
fit both definitions but are not corrected or compensated for by the
adaptive fuel control system to be monitored as ``other emissions
control devices'' rather than as comprehensive components. A typical
device that would fall under this category instead of the comprehensive
components category because of this delineation would be a swirl
control valve system. Such delineation is necessary because such
emissions control components generally require more thorough monitoring
than comprehensive components to ensure low emissions levels throughout
an engine's life. Further, emissions control components that are not
compensated for by the fuel control system as they age or deteriorate
can have a larger impact on tailpipe emissions than is typical of
comprehensive components that are corrected for by the fuel control
system as they deteriorate.
Note that the Administrator does not foresee any outcome where a
promising new emissions control technology would be prohibited based
solely on the lack of an OBD monitoring strategy for it. Instead, we
want to instill in manufacturers the need to consider OBD monitoring
when developing any new emissions control technology. Further, we want
to instill in manufacturers the sense that an OBD monitoring strategy
will, one day, be necessary so a plan for such should exist prior to
introducing the technology on new products.
b. Other Emissions Control System Monitoring Requirements/Conditions
We are proposing that, for other emission control systems that are:
(1) Not identified or addressed in sections II.B through II.D.4--e.g.,
hydrocarbon traps, HCCI control systems; or, (2) identified or
addressed in section II.D.4 but not corrected or compensated for by an
adaptive control system--e.g., swirl control valves, manufacturers
would be required to submit a plan for Administrator approval of the
monitoring strategy, the malfunction criteria, and the monitoring
conditions prior to introduction on a production engine. Administrator
approval of the plan would be based on the effectiveness of the
monitoring strategy, the robustness of the malfunction criteria, and
the frequency of meeting the necessary monitoring conditions.
We are also proposing that, for engines that use emissions control
systems that alter intake air flow or cylinder charge characteristics
by actuating valve(s), flap(s), etc., in the intake air delivery system
(e.g., swirl control valve systems), the manufacturers, in addition to
meeting the requirements above, may elect to have the OBD system
monitor the shaft to which all valves in one intake bank are physically
attached rather than monitoring the intake air flow, cylinder charge,
or individual valve(s)/flap(s) for proper functional response. For non-
metal shafts or segmented shafts, the monitor must verify all shaft
segments for proper functional response (e.g., by verifying the segment
or portion of the shaft furthest from the actuator functions properly).
For systems that have more than one shaft to operate valves in multiple
intake banks, manufacturers are not required to add more than one set
of detection hardware (e.g., sensor, switch) per intake bank to meet
this requirement.

[[Page 3238]]

6. Exceptions to Monitoring Requirements
a. Background
Under some conditions, the reliability of specific monitors may be
diminished significantly. Therefore, we are proposing to allow
manufacturers to disable the affected monitors when these conditions
are encountered in-use. These include situations of extreme conditions
(e.g., very low ambient temperatures, high altitudes) and of periods
where default modes of operation are active (e.g., when a tire pressure
problem is detected). In some of these cases, we may allow
manufacturers to revise the emission malfunction threshold to ensure
the most reliable monitoring performance.
b. Requirements for Exceptions to Monitoring
The Administrator may revise the emission threshold for any
monitor, or revise the PM filtering performance malfunction criteria
for DPFs to exclude detection of specific failure modes such as
partially melted substrates, if the most reliable monitoring method
developed requires a higher threshold or, in the case of PM filtering
performance, the exclusion of specific failure modes, to prevent
significant errors of commission in detecting a malfunction. The
Administrator would notify the industry of any such revisions to ensure
that all manufacturers would be able to implement OBD on an equal
basis. In other words, we would not allow one manufacturer to revise a
specific monitoring threshold upwards while insisting that another meet
the proposed threshold.
Manufacturers may disable an OBD system monitor at ambient engine
start temperatures below 20 degrees Fahrenheit (low ambient temperature
conditions may be determined based on intake air or engine coolant
temperature at engine start) or at elevations higher than 8000 feet
above sea level. To do so, the manufacturer would have to submit data
and/or engineering analyses that demonstrate that monitoring would be
unreliable during the disable conditions. A manufacturer may request
that an OBD system monitor be disabled at other ambient engine start
temperatures by submitting data and/or engineering analyses demonstrating
that misdiagnosis would occur at the given ambient temperatures due to
their effect on the component itself (e.g., component freezing).
Manufacturers may disable an OBD system monitor when the fuel level
is 15 percent or less of the nominal fuel tank capacity for those
monitors that can be affected by low fuel level or running out of fuel
(e.g., misfire detection). To do so, the manufacturer would have to
submit data and/or engineering analyses that demonstrate that both
monitoring at the given fuel levels would be unreliable, and the OBD
system is still able to detect a malfunction if the component(s) used
to determine fuel level indicates erroneously a fuel level that causes
the disablement.
Manufacturers may disable OBD monitors that can be affected by
vehicle battery or system voltage levels. For an OBD monitor affected
by low vehicle battery or system voltages, manufacturers may disable
monitoring when the battery or system voltage is below 11.0 Volts.
Manufacturers may use a voltage threshold higher than 11.0 Volts to
disable monitors but would have to submit data and/or engineering
analyses that demonstrate that monitoring at those voltages would be
unreliable and that either operation of a vehicle below the disablement
criteria for extended periods of time is unlikely or the OBD system
monitors the battery or system voltage and would detect a malfunction
at the voltage used to disable other monitors.
For monitoring systems affected by high vehicle battery or system
voltages, manufacturers may disable monitoring when the battery or
system voltage exceeds a manufacturer-defined voltage. To do so, the
manufacturer would have to submit data and/or engineering analyses that
demonstrate that monitoring above the manufacturer-defined voltage
would be unreliable and that either the electrical charging system/
alternator warning light would be illuminated (or voltage gauge would
be in the ``red zone'') or the OBD system monitors the battery or
system voltage and would detect a malfunction at the voltage used to
disable other monitors.
A manufacturer may also disable affected OBD monitors in vehicles
designed to accommodate the installation of power take off (PTO) units
provided disablement occurs only while the PTO unit is active and the
OBD readiness status is cleared by the onboard computer (i.e., all
monitors set to indicate ``not complete'') while the PTO unit is
activated (see section II.F.4 below). If the disablement occurs, the
readiness status may be restored, when the disablement ends, to its
state prior to PTO activation.

E. A Standardized Method To Measure Real World Monitoring Performance

As was noted in section II.A.3, manufacturers determine the most
appropriate times to run the non-continuous OBD monitors. This way,
they are able to make their OBD evaluation either at the operating
condition when an emissions control system is active and its
operational status can best be evaluated, and/or at the operating
condition when the most accurate evaluation can be made (e.g., highly
transient conditions or extreme conditions can make evaluation
difficult). Importantly, manufacturers are prohibited from using a
monitoring strategy that is so restrictive such that it rarely or never
runs. To help protect against monitors that rarely run, we are
proposing an ``in-use monitor performance ratio'' requirement as
described here.
The set of operating conditions that must be met so that an OBD
monitor can run are called the ``enable criteria'' for that given
monitor. These enable criteria are often different for different
monitors and may well be different for different types of engines. A
large diesel engine intended for use in a Class 8 truck would be
expected to see long periods of relatively steady-state operation while
a smaller engine intended for use in an urban delivery truck would be
expected to see a lot of transient operation. Manufacturers will need
to balance between a rather loose set of enable criteria for their
engines and vehicles given the very broad range of operation HD highway
engines see and a tight set of enable criteria given the desire for
greater monitor accuracy. Manufacturers would be required to design
these enable criteria so that the monitor:
? Is robust (i.e., accurate at making pass/fail decisions);
? Runs frequently in the real world; and,
? In general, also runs during the FTP heavy-duty transient cycle.
If designed incorrectly, these enable criteria may be either too
broad and result in inaccurate monitors, or overly restrictive thereby
preventing the monitor from executing frequently in the real world.
Since the primary purpose of an OBD system is to monitor for and
detect emission-related malfunctions while the engine is operating in
the real world, a standardized methodology for quantifying real world
performance would be beneficial to both EPA and manufacturers.
Generally, in determining whether a manufacturer's monitoring
conditions are sufficient, a manufacturer would discuss the proposed
monitoring conditions with EPA staff. The finalized conditions would be
included in the certification applications and submitted to EPA staff
who would review the conditions and make determinations on a case-by-case

[[Page 3239]]

basis based on the engineering judgment of the staff. In cases where we
are concerned that the documented conditions may not be met during
reasonable in-use driving conditions, we would most likely ask the
manufacturer for data or other engineering analyses used by the
manufacturer to determine that the conditions would occur in-use. In
proposing a standardized methodology for quantifying real world
performance, we believe this review process can be done more
efficiently than would occur otherwise. Furthermore, it would serve to
ensure that all manufacturers are held to the same standard for real
world performance. Lastly, we want review procedures that will ensure
that monitors operate properly and frequently in the field.
Therefore, we are proposing that all manufacturers be required to
use a standardized method for determining real world monitoring
performance and to hold manufacturers liable if monitoring occurs less
frequently than a minimum acceptable level, expressed as minimum
acceptable in-use performance ratio. We are also proposing that
manufacturers be required to implement software in the onboard computer
to track how often several of the major monitors (e.g., catalyst, EGR,
CDPF, other diesel aftertreatment devices) execute during real world
driving. The onboard computer would keep track of how many times each
of these monitors has executed and how much the engine has been
operated. By measuring both of these values, the ratio of monitor
operation relative to engine operation can be calculated to determine
monitoring frequency.
The proposed minimum acceptable frequency requirement would apply
to many but not all of the OBD monitors. We are proposing that monitors
be required to operate either continuously, once per drive cycle, or,
in a few cases, multiple times per drive cycle (i.e., whenever the
proper monitoring conditions are present). For components or systems
that are more likely to experience intermittent failures or failures
that can routinely happen in distinct portions of an engine's operating
range (e.g., only at high engine speed and load, only when the engine
is cold or hot), monitors would be required to operate continuously.
Examples of continuous monitors include the fuel system monitor and
most electrical/circuit continuity monitors. For components or systems
that are less likely to experience intermittent failures or failures
that only occur in specific vehicle operating regions or for components
or systems where accurate monitoring can only be performed under
limited operating conditions, monitors would be required to run once
per drive cycle. Examples of once per drive cycle monitors typically
include gasoline catalyst monitors, evaporative system leak detection
monitors, and output comprehensive component functional monitors. For
components or systems that are routinely used to perform functions that
are crucial to maintaining low emissions but may still require
monitoring under fairly limited conditions, monitors would be required
to run each and every time the manufacturer-defined enable conditions
are present. Examples of multiple times per drive cycle monitors
typically include input comprehensive component rationality monitors
and some exhaust aftertreatment monitors.
Monitors required to run continuously, by definition, would always
be running, thereby making a minimum frequency requirement moot. The
new frequency requirement would essentially apply only to those
monitors that are designated as once per drive cycle or multiple times
per drive cycle monitors. For all of these monitors, manufacturers
would be required to define monitoring conditions that ensure adequate
frequency in-use. Specifically, the monitors would need to run often
enough so that the measured monitor frequency on in-use engines would
exceed the minimum acceptable frequency. However, even though the
minimum frequency requirement would apply to nearly all once per drive
cycle and multiple times per drive cycle monitors, manufacturers would
only be required to implement software to track and report the in-use
frequency for a few of the major monitors. These few monitors generally
represent the major emissions control components and the ones with the
most limited enable criteria.
We believe that OBD monitors should run frequently to ensure early
detection of emissions-related malfunctions and, consequently, to
maintain low emissions. Allowing malfunctions to continue undetected
and unrepaired for long periods of time allows emissions to increase
unnecessarily. Frequent monitoring can also help to ensure detection of
intermittent emissions-related malfunctions (i.e., those that are not
continuously present but occur sporadically for days and even weeks at
a time). The nature of mechanical and electrical systems is that
intermittent malfunctions can and do occur. The less frequent the
monitoring, the less likely these malfunctions will be detected and
repaired. Additionally, for both intermittent and continuous
malfunctions, earlier detection is equivalent to preventative
maintenance in that the original malfunction can be detected and
repaired prior to it causing subsequent damage to other components.
This can help vehicle operators avoid more costly repairs that could
have resulted had the first malfunction gone undetected.
Infrequent monitoring can also have an impact on the service and
repair industry. Specifically, monitors that have unreasonable or
overly restrictive enable conditions could hinder vehicle repair
services. In general, upon completing an OBD-related repair to an
engine, a technician will attempt to verify that the repair has indeed
fixed the problem. Ideally, a technician will operate the vehicle in a
manner that will exercise the appropriate OBD monitor and allow the OBD
system to confirm that the malfunction is no longer present. This
affords a technician the highest level of assurance that the repair was
indeed successful. However, OBD monitors that operate infrequently are
difficult to exercise and, therefore, technicians may not be able (or
may not be likely) to perform such post-repair evaluations. Despite the
service information availability requirements we are proposing--
requirements that manufacturers make all of their service and repair
information available to all technicians, including the information
necessary to exercise OBD monitors--technicians would still find it
difficult to exercise monitors that require infrequently encountered
engine operating conditions (e.g., abnormally steady constant speed
operation for an extended period of time). Additionally, to execute OBD
monitors in an expeditious manner or to execute monitors that would
require unusual or infrequently encountered conditions, technicians may
be required to operate the vehicle in an unsafe manner (e.g., at
freeway speeds on residential streets or during heavy traffic). If
unsuccessful in executing these monitors, technicians may even take
shortcuts in attempting to validate the repair while maintaining a
reasonable cost for customers. These shortcuts would likely not be as
thorough in verifying repairs and could increase the chance that
improperly repaired engines would be returned to the vehicle owner or
additional repairs would be performed just to ensure the problem is
fixed. In the end, monitors that operate less frequently can result in
unnecessary costs and inconvenience to both vehicle owners and technicians.

[[Page 3240]]

1. Description of Software Counters to Track Real World Performance
As stated above, manufacturers would be required to track monitor
peformance by comparing the number of monitoring events (i.e., how
often each monitor has run) to the number of driving events (i.e., how
often has the vehicle been operated). The ratio of these two numbers
would give an indication of how often the monitor is operating relative
to vehicle operation. In equation form, this can be stated as:
[GRAPHIC]
[TIFF OMITTED] TP24JA07.004

To ensure that all manufacturers are tracking in-use performance in
the same manner, we are proposing very detailed requirements for
defining and incrementing both the numerator and denominator of this
ratio. Manufacturers would be required to keep track of separate
numerators and denominators for each of the major monitors, and to
ensure that the data are saved every time the engine is shut off. The
numerators and denominators would be reset to zero only in extreme
circumstances when the non-volatile memory has been cleared (e.g., when
the onboard computer has been reprogrammed in the field or when the
onboard computer memory has been corrupted). The values would not be
reset to zero during normal occurrences such as clearing of stored DTCs
or performing routine service or maintenance.
Further, the numerator and denominator would be structured such
that their maximum values would be 65,535 which is the maximum number
that can be stored in a 2-byte location. This would ensure that
manufacturers allocate sufficient and consistent memory space in the
onboard computer. If either the numerator or denominator for a
particular monitor reaches the maximum value, both values for that
particular monitor would be divided by two before counting resumes. In
general, the numerator and denominator would only be allowed to
increment a maximum of once per drive cycle because most of the major
monitors are designed to operate only once per drive cycle.
Additionally, incrementing of both the numerator and denominator for a
particular monitor would be disabled (i.e., paused but the stored
values would not be erased or reset) only when a problem has been
detected (i.e., a pending or MIL-on DTC has been stored) that prevents
the monitor from executing. Once the problem is no longer detected and
any stored DTCs associated with the problem have been erased, either
through the allowable self-clearing process or upon command by a
technician via a scan tool, incrementing of both the numerator and
denominator would resume.
SAE has developed standards for storing and reporting the data to a
generic scan tool. This would help ensure that all manufacturers report
the data in an identical manner which should ease data collection in
the field.
a. Number of Monitoring Events (``Numerator'')
For the numerator, manufacturers would be required to keep a
separate numeric count of how often each of the particular monitors has
operated. More specifically, manufacturers would have to implement a
software counter that increments by one every time the particular
monitor meets all of the enable/monitoring conditions for a long enough
period of time such that a malfunctioning component would have been
detected. For example, if a manufacturer requires a vehicle to be
warmed-up and at idle for 20 seconds continuously to detect a
malfunctioning catalyst, the catalyst monitor numerator could only be
incremented if the vehicle actually operates simultaneously in all of
those conditions. If the vehicle is operated in some but not all of the
conditions (e.g., at idle but not warmed-up), the numerator would not
be allowed to increment because the monitor would not have been able to
detect a malfunctioning catalyst since all of the conditions were not
satisfied simultaneously.
Another complication is the difference between a monitor reaching a
``pass'' or ``fail'' decision. At first glance, it would appear that a
manufacturer should simply increment the numerator anytime the
particular monitor reaches a decision, be it ``pass'' or ``fail''.
However, monitoring strategies may have a different set of criteria
that must be met to reach a ``pass'' decision versus a ``fail''
decision. As a simple example, a manufacturer may appropriately require
only 10 seconds of operation at idle to reach a ``pass'' decision but
require 30 seconds of operation at idle to reach a ``fail'' decision.
Manufacturers would not be allowed to increment the numerator if the
vehicle had idled for 10 seconds and reached a ``pass'' decision since
insufficient time had passed to allow for a possible ``fail'' decision.
This is necessary because the primary function of OBD systems is to
detect malfunctions (i.e., to correctly reach ``fail'' decisions, not
``pass'' decisions) and, thus, the real world ability of the monitors
to detect malfunctions is the parameter we want most to measure.
Therefore, monitors with different criteria to reach a ``pass''
decision versus a ``fail'' decision would not be allowed to increment
the numerator solely upon satisfying the ``pass'' criteria.
The correct implementation of the numerator counters by
manufacturers is imperative to ensure a reliable measure for
determining real world performance. ``Overcounting'' would falsely
indicate the monitor is executing more often than it really is, while
``undercounting'' would make it appear as if the monitor is not running
as often as it really is. Manufacturers would be required to describe
their numerator incrementing strategy in their certification
documentation and to verify the proper performance of their strategy
during production vehicle evaluation testing.
b. Number of Driving Events (``Denominator'')
We are also proposing that manufacturers separately track how often
the engine is operated. Basically, the denominator would be a counter
that increments by one each time the engine is operated. We are
proposing that the denominator counter be incremented by one only if
several criteria are satisfied during a single drive cycle. This allows
very short trips or trips during extreme conditions such as very cold
temperatures or very high altitude to be filtered out and excluded from
the count. This is appropriate because these are also conditions where
most OBD monitors are neither expected nor required to operate.
Specifically, the denominator would be incremented if, on a single
key start, the following criteria were satisfied while ambient
temperature remained above 20 degrees Fahrenheit and altitude remained
below 8,000 feet:
? Minimum engine run time of 10 minutes;

[[Page 3241]]

? Minimum of 5 minutes, cumulatively, of operation at
vehicle speeds greater than 25 miles-per-hour for gasoline engines or
calculated load greater than 15 percent for diesel engines; and
? At least one continuous idle for a minimum of 30 seconds encountered.
We intend to work with industry to collect data during the first
few years of implementation and make any adjustments, if necessary, to
the criteria used to increment the denominator to ensure that the in-
use performance ratio provides a meaningful measure of in-use
monitoring performance.
2. Proposed Performance Tracking Requirements
a. In-use Monitoring Performance Ratio Definition
For monitors required to meet the in-use performance tracking
requirements,\44\ we are proposing that the incrementing of numerators
and denominators and the calculation of the in-use performance ratio be
done in accordance with the following specifications.
---------------------------------------------------------------------------

\44\ These monitors, as presented in section II.A.3, are, for
diesel engines: the NMHC catalyst, the CDPF system, the
NO_X adsorber system, the NO_X converting
catalyst system, and the boost system; and, for gasoline engines:
the catalyst, the evaporative system, and the secondary air system;
and, for all engines, the exhaust gas sensors, the EGR system, and
the VVT system.
---------------------------------------------------------------------------

The numerator(s) would be defined as a measure of the number of
times a vehicle has been operated such that all monitoring conditions
necessary for a specific monitor to detect a malfunction have been
encountered. Except for systems using alternative statistical MIL
illumination protocols, the numerator is to be incremented by an
integer of one. The numerator(s) may not be incremented more than once
per drive cycle. The numerator(s) for a specific monitor would be
incremented within 10 seconds if and only if the following criteria are
satisfied on a single drive cycle:
? Every monitoring condition necessary for the monitor of
the specific component to detect a malfunction and store a pending DTC
has been satisfied, including enable criteria, presence or absence of
related DTCs, sufficient length of monitoring time, and diagnostic
executive priority assignments (e.g., diagnostic ``A'' must execute
prior to diagnostic ``B''). For the purpose of incrementing the
numerator, satisfying all the monitoring conditions necessary for a
monitor to determine that the component is passing may not, by itself,
be sufficient to meet this criteria.
? For monitors that require multiple stages or events in a
single drive cycle to detect a malfunction, every monitoring condition
necessary for all events to have completed must be satisfied.
? For monitors that require intrusive operation of
components to detect a malfunction, a manufacturer would be required to
request Administrator approval of the strategy used to determine that,
had a malfunction been present, the monitor would have detected the
malfunction. Administrator approval of the request would be based on
the equivalence of the strategy to actual intrusive operation and the
ability of the strategy to determine accurately if every monitoring
condition was satisfied as necessary for the intrusive event to occur.
? For the secondary air system monitor, the three criteria
above are satisfied during normal operation of the secondary air
system. Monitoring during intrusive operation of the secondary air
system later in the same drive cycle solely for the purpose of
monitoring may not, by itself, be sufficient to meet these criteria.
The third bullet item above requires explanation. There may be
monitors, and there have been monitors in light-duty, designed to use
what could be termed a two stage or two step process. The first step is
usually a passive and/or short evaluation that can be used to ``pass''
a properly working component where ``pass'' refers to evaluating the
component and determining that it is not malfunctioning. The second
step is usually an intrusive and/or longer evaluation that is necessary
to ``fail'' a malfunctioning component or ``pass'' a component nearing
the point of failure. An example of such an approach might be an
evaporative leak detection monitor that uses an intrusive vacuum pull-
down/bleed-up evaluation during highway cruise conditions. If the
evaporative system is sealed tight, the monitor ``passes'' and is done
with testing for the given drive cycle. If the monitor senses a leak
close to the required detection limit, the monitor does not ``pass''
and an internal flag is stored that will trigger the second stage of
the test during the next cold start when a more accurate evaluation can
be conducted. On the next cold start, provided the internal flag is
set, an intrusive vacuum pull-down/bleed up monitor might be conducted
during engine idle a very short time after the cold start. This second
evaluation stage, being at idle and cold, gives a more accurate
indication of the evaporative system's integrity and provides for a
more accurate decision regarding the presence and size of a leak.
In this example, the second stage of this monitor would run less
frequently in real use than the first stage since it is activated only
on those occasions where the first stage suggests that a leak may be
present (which most cars will not have). The rate-based tracking
requirements are meant to give a measure of how often a monitor could
detect a malfunction. To know the right answer, we need to know how
often the first stage is running and could ``fail'', thus triggering
the second stage, and then how often the second stage is completing. If
we track only the first stage, we would get a false indication of how
often the monitor could really detect a leak. But, if we track only the
second stage, most cars would never increment the counter since most
cars do not have leaks and would not trigger stage two.
In considering this, we see two possible solutions: (1) Always
activate the second stage evaluation in which case there would be an
intrusive monitor being performed that does not really need to be
performed; or, (2) implement a ``ghost'' monitor that pretends that the
first stage evaluation triggers the second stage evaluation and then
also looks for when the second stage evaluation could have completed
had it been necessary. The third bullet item in the list above requires
that, if a manufacturer intends to implement a two stage monitor and
intends to implement such a ``ghost'' monitor as described here for
rate based tracking, approval must be sought for doing so to make sure
we agree that you are doing it correctly and properly.
For monitors that can generate results in a ``gray zone'' or ``non-
detection zone'' (i.e., results that indicate neither a passing system
nor a malfunctioning system) or in a ``non-decision zone'' (e.g.,
monitors that increment and decrement counters until a pass or fail
threshold is reached), the manufacturer would be responsible for
incrementing the numerator appropriately. In general, the numerator
should not be incremented when the monitor indicates a result in the
``non-detection zone'' or prior to the monitor reaching a decision.
When necessary, the Administrator would consider data and/or
engineering analyses submitted by the manufacturer demonstrating the
expected frequency of results in the ``non-detection zone'' and the
ability of the monitor to determine accurately, had an actual
malfunction been present, whether or not the monitor would have
detected a malfunction instead of a result in the ``non-detection zone.''

[[Page 3242]]

For monitors that run or complete their evaluation with the engine
off, the numerator must be incremented either within 10 seconds of the
monitor completing its evaluation in the engine off state, or during
the first 10 seconds of engine start on the subsequent drive cycle.
Manufacturers using alternative statistical MIL illumination
protocols for any of the monitors that require a numerator would be
required to increment the numerator(s) appropriately. The manufacturer
may be required to provide supporting data and/or engineering analyses
demonstrating both the equivalence of their incrementing approach to
the incrementing specified above for monitors using the standard MIL
illumination protocol, and the overall equivalence of their
incrementing approach in determining that the minimum acceptable in-use
performance ratio has been satisfied.
Regarding the denominator(s), defined as a measure of the number of
times a vehicle has been operated, we are proposing that it also be
incremented by an integer of one. The denominator(s) may not be
incremented more than once per drive cycle. The general denominator and
the denominators for each monitor would be incremented within 10
seconds if and only if the following criteria are satisfied on a single
drive cycle during which ambient temperature remained at or above 20
degrees Fahrenheit and altitude remained below 8,000 feet:
? Cumulative time since the start of the drive cycle is
greater than or equal to 600 seconds (10 minutes);
? Cumulative gasoline engine operation at or above 25 miles
per hour or diesel engine operation at or above 15 percent calculated
load, either of which occurs for greater than or equal to 300 seconds
(5 minutes); and
? Continuous engine operation at idle (e.g., accelerator
pedal released by driver and vehicle speed less than or equal to one
mile per hour) for greater than or equal to 30 seconds.
In addition to the requirements above, the evaporative system
monitor denominator(s) must be incremented if and only if:
? Cumulative time since the start of the drive cycle is
greater than or equal to 600 seconds (10 minutes) while at an ambient
temperature of greater than or equal to 40 degrees Fahrenheit but less
than or equal to 95 degrees Fahrenheit; and
? Engine cold start occurs with engine coolant temperature
at engine start greater than or equal to 40 degrees Fahrenheit but less
than or equal to 95 degrees Fahrenheit and less than or equal to 12
degrees Fahrenheit higher than ambient temperature at engine start.
In addition to the requirements above, the denominator(s) for the
following monitors must be incremented if and only if the component or
strategy is commanded ``on'' for a time greater than or equal to 10 seconds:
? Gasoline secondary air system;
? Cold start emission reduction strategy;
? Components or systems that operate only at engine start-up
(e.g., glow plugs, intake air heaters) and are subject to monitoring
under ``other emission control systems'' (section II.D.5) or
comprehensive component output components (see section II.D.4).
For purposes of determining this commanded ``on'' time, the OBD
system may not include time during intrusive operation of any of the
components or strategies later in the same drive cycle solely for the
purposes of monitoring.
In addition to the requirements above, the denominator(s) for the
monitors of the following output components (except those operated only
at engine start-up as outlined above) must be incremented if and only
if the component is commanded to function (e.g., commanded ``on'',
``open'', ``closed'', ``locked'') two or more times during the drive
cycle or for a time greater than or equal to 10 seconds, whichever
occurs first:
? Variable valve timing and/or control system
? ``Other emission control systems''
? Comprehensive component (output component only, e.g.,
turbocharger waste-gates, variable length manifold runners)
For monitors of the following components, the manufacturer may use
alternative or additional criteria to that set forth above for
incrementing the denominator. To do so, the manufacturer would need to
be able to demonstrate that the criteria would be equivalent to the
criteria outlined above at measuring the frequency of monitor operation
relative to the amount of engine operation:
? Engine cooling system input components (section II.D.2)
? ``Other emission control systems'' (section II.D.5)
? Comprehensive component input components that require
extended monitoring evaluation (section II.D.4, e.g., stuck fuel level
sensor rationality)
For monitors of the following components or other emission controls
that experience infrequent regeneration events, the manufacturer may
use alternative or additional criteria to that set forth above for
incrementing the denominator. To do so, the manufacturer would need to
demonstrate that the criteria would be equivalent to the criteria
outlined above at measuring the frequency of monitor operation relative
to the amount of engine operation:
? Oxidation catalysts
? Diesel particulate filters
For hybrid engine systems, engines that employ alternative engine
start hardware or strategies (e.g., integrated starter and generators),
or alternative fueled engines (e.g., dedicated, bi-fuel, or dual-fuel
applications), the manufacturer may request Administrator approval to
use alternative criteria to that set forth above for incrementing the
denominator. In general, approval would not be given for alternative
criteria that only employ engine shut off at or near idle/vehicle
stationary conditions. Approval of the alternative criteria would be
based on the equivalence of the alternative criteria at determining the
amount of engine operation relative to the measure of conventional
engine operation in accordance with the criteria above.
The numerators and denominators may need to be disabled at some
times. To do this, within 10 seconds of a malfunction being detected
(i.e., a pending, MIL-on, or active DTC being stored) that disables a
monitor required to meet the performance tracking requirements,\45\ the
OBD system must disable further incrementing of the corresponding
numerator and denominator for each monitor that is disabled. When the
malfunction is no longer detected (e.g., the pending DTC is erased
through self-clearing or through a scan tool command), incrementing of
all corresponding numerators and denominators should resume within 10
seconds. Also, within 10 seconds of the start of a power takeoff unit
(PTO) that disables a monitor required to meet the performance tracking
requirements, the OBD system should disable further incrementing of the
corresponding numerator and denominator for each monitor that is
disabled. When the PTO operation ends, incrementing of all
corresponding numerators and denominators should resume within 10
seconds. The OBD system must disable further incrementing of all numerators

[[Page 3243]]

and denominators within 10 seconds if a malfunction has been detected
in any component used to determine if: vehicle speed/calculated load;
ambient temperature; elevation; idle operation; engine cold start; or,
time of operation has been satisfied, and the corresponding pending DTC
has been stored. Incrementing of all numerators and denominators should
resume within 10 seconds when the malfunction is no longer present
(e.g., pending DTC erased through self-clearing or by a scan tool command).
---------------------------------------------------------------------------

\45\ These monitors, as presented in section II.A.3, are, for
diesel engines: the NMHC catalyst, the CDPF system, the
NO_X adsorber system, the NO_X converting
catalyst system, and the boost system; and, for gasoline engines:
the catalyst, the evaporative system, and the secondary air system;
and, for all engines, the exhaust gas sensors, the EGR system, and
the VVT system.
---------------------------------------------------------------------------

The in-use performance monitoring ratio itself is defined as the
numerator for the given monitor divided by the denominator for that monitor.
b. Standardized Tracking and Reporting of Monitor Performance
We are proposing that the OBD system separately report an in-use
monitor performance numerator and denominator for each of the following
components:
? For diesel engines: NMHC catalyst bank 1, NMHC catalyst
bank 2, NO_X catalyst bank 1, NO_X catalyst bank 2,
exhaust gas sensor bank 1, exhaust gas sensor bank 2, EGR/VVT system,
DPF system, turbo boost control system, and the NO_X
adsorber. The OBD system must also report a general denominator and an
ignition cycle counter in the standardized format discussed below and
in section II.F.5.
? For gasoline engines: catalyst bank 1, catalyst bank 2,
oxygen sensor bank 1, oxygen sensor bank 2, evaporative leak detection
system, EGR/VVT system, and secondary air system. The OBD system must
also report a general denominator and an ignition cycle counter in the
standardized format specified below and in section II.F.5.
The OBD system would be required to report a separate numerator for
each of the components listed in the above bullet lists. For specific
components or systems that have multiple monitors that are required to
be reported under section II.B--e.g., exhaust gas sensor bank 1 may
have multiple monitors for sensor response or other sensor
characteristics--the OBD system should separately track numerators and
denominators for each of the specific monitors and report only the
corresponding numerator and denominator for the specific monitor that
has the lowest numerical ratio. If two or more specific monitors have
identical ratios, the corresponding numerator and denominator for the
specific monitor that has the highest denominator should be reported
for the specific component. The numerator(s) must be reported in
accordance with the specifications in section II.F.5.
The OBD system would also be required to report a separate
denominator for each of the components listed in the above bullet
lists. The denominator(s) must be reported in accordance with the
specifications in section II.F.5.
Similarly, for the in-use performance ratio, determining which
corresponding numerator and denominator to report as required for
specific components or systems that have multiple monitors that are
required to be reported--e.g., exhaust gas sensor bank 1 may have
multiple monitors for sensor response or other sensor
characteristics'the ratio should be calculated in accordance with the
specifications in section II.F.5.
The ignition cycle counter is defined as a counter that indicates
the number of ignition cycles a vehicle has experienced. The ignition
cycle counter must also be reported in accordance with the
specifications in section II.F.5. The ignition cycle counter, when
incremented, should be incremented by an integer of one. The ignition
cycle counter may not be incremented more than once per ignition cycle.
The ignition cycle counter should be incremented within 10 seconds if
and only if the engine exceeds an engine speed of 50 to 150 rpm below
the normal, warmed-up idle speed (as determined in the drive position
for vehicles equipped with an automatic transmission) for at least two
seconds plus or minus one second. The OBD system should disable further
incrementing of the ignition cycle counter within 10 seconds if a
malfunction has been detected in any component used to determine if
engine speed or time of operation has been satisfied and the
corresponding pending DTC has been stored. The ignition cycle counter
may not be disabled from incrementing for any other condition.
Incrementing of the ignition cycle counter should resume within 10
seconds after the malfunction is no longer present (e.g., pending DTC
erased through self-clearing or by a scan tool command).

F. Standardization Requirements

The heavy-duty OBD regulation would include requirements for
manufacturers to standardize certain features of the OBD system.
Effective standardization assists all repair technicians in diagnosing
and repairing malfunctions by providing equal access to essential
repair information, and requires structuring the information in a
common format from manufacturer to manufacturer. Additionally, the
standardization would help to facilitate the potential use of OBD
checks in heavy-duty inspection and maintenance programs.
Among the features that would be standardized under the proposed
heavy-duty OBD regulation include:
? The diagnostic connector, the computer communication protocol;
? The hardware and software specifications for tools used by
service technicians;
? The information communicated by the onboard computer and
the methods for accessing that information;
? The numeric designation of the DTCs stored when a
malfunction is detected; and,
? The terminology used by manufacturers in their service manuals.
Our proposal would require that only a certain minimum set of
emissions-related information be made available through the
standardized format, protocol, and connector. We are not limiting
engine manufacturers as to what protocol they use for engine control,
communication between onboard computers, or communication to
manufacturer-specific scan tools or test equipment. Further, we are not
prohibiting engine manufacturers from equipping the vehicle with
additional diagnostic connectors or protocols as required by other
suppliers or purchasers. For example, fleets that use data logging or
other equipment that requires the use of SAE J1587 communication and
connectors could still be installed and supported by the engine and
vehicle manufacturers. The OBD rules would only require that engine
manufacturers also equip their vehicles with a specific connector and
communication protocol that meet the standardized requirements to
communicate a minimum set of emissions-related diagnostic, service and,
potentially, inspection information.
Additionally, our proposal includes a phase-in of one engine family
meeting the requirements of OBD in the model years 2010 through 2012.
Because non-compliant engines would not require the proposed
standardization features, truck and coach builders could be faced with
several integration issues when building product in 2010 through 2012.
Specifically, they could be faced with designing their vehicles to
accommodate a standardized MIL, diagnostic connector, and communication
protocol when using a compliant engine yet to not accommodate those
features when using a non-compliant engine. This outcome could easily
arise since only one engine-family per manufacturer would be compliant
and, therefore, a given truck

[[Page 3244]]

designed to accommodate several engines from several engine
manufacturers would very likely need to accommodate a compliant engine
from manufacturer A and a non-compliant engine from manufacturer B. It
should be noted that engine choices are typically driven by the end
user--the truck buyer--and not by the truck or coach builder. For that
reason, the truck builder must accommodate all possible engines for the
truck size and cannot necessarily demand from the engine manufacturer a
compliant versus a non-compliant engine.
As a result, rather than force truck and coach builders to
accommodate two different systems and risk incompatibilities, we are
proposing to exempt the 2010 through 2012 model year engines from
meeting certain standardization requirements of OBD. This should allow
truck and coach builders to integrate engines in the same manner as
done currently and then to switch over to integrating a single system
in 2013 when all engines are required to meet all of the
standardization requirements of OBD. The proposed implementation
schedule for standardization features is shown in Table II.G-2.
1. Reference Documents
We are proposing that OBD systems comply with the following
provisions laid out in the following Society of Automotive Engineers
(SAE) and/or International Organization of Standards (ISO) documents
that are or would be incorporated by reference (IBR) into federal regulation:

Table II.F--1. Reference Documents for Over 14,000 Pound OBD
----------------------------------------------------------------------------------------------------------------
Document No. Document title Date Comment
----------------------------------------------------------------------------------------------------------------
SAE J1962................. ``Diagnostic Connector--Equivalent April 2002.......... Updated IBR.
to ISO/DIS 15031-3: December 14,
2001''.
SAE J1930................. ``Electrical/Electronic Systems April 2002.......... Updated IBR.
Diagnostic Terms, Definitions,
Abbreviations, and Acronyms--
Equivalent to ISO/TR 15031-2:
April 30, 2002''.
SAE J1978................. ``OBD II Scan Tool--Equivalent to April 2002.......... Updated IBR.
ISO/DIS 15031-4: December 14,
2001''.
SAE J1979................. ``E/E Diagnostic Test Modes-- April 2002.......... Updated IBR.
Equivalent to ISO/DIS 15031-5:
April 30, 2002''.
SAE J2012................. ``Diagnostic Trouble Code April 2002.......... Updated IBR.
Definitions--Equivalent to ISO/DIS
15031-6: April 30, 2002''.
SAE J1939................. ``Recommended Practice for a Serial 2005 Edition, March Updated IBR.
Control and Communications Vehicle 2005.
Network,'' and the associated
subparts included in SAE HS-1939,
``Truck and Bus Control and
Communications Network Standards
Manual''.
SAE J2403................. ``Medium/Heavy-Duty E/E Systems August 2004......... New IBR.
Diagnosis Nomenclature''.
SAE J2534................. ``Recommended Practice for Pass- February 2002....... New IBR.
Thru Vehicle Reprogramming''.
ISO 15765-4:2001.......... ``Road Vehicles--Diagnostics on December 2001....... New IBR.
Controller Area Network (CAN)--
Part 4: Requirements for emission-
related systems''.
----------------------------------------------------------------------------------------------------------------

Copies of these SAE materials may be obtained from Society of
Automotive Engineers International, 400 Commonwealth Dr., Warrendale,
PA, 15096-0001. Copies of these ISO materials may be obtained from the
International Organization for Standardization, Case Postale 56, CH-
1211 Geneva 20, Switzerland.
2. Diagnostic Connector Requirements
We are proposing that a standard data link connector conforming to
either SAE J1962 or SAE J1939-13 specifications (except as noted below)
would have to be included in each vehicle. The connector would have to
be located in the driver's side foot-well region of the vehicle
interior in the area bound by the driver's side of the vehicle and the
driver's side edge of the center console (or the vehicle centerline if
the vehicle does not have a center console) and at a location no higher
than the bottom of the steering wheel when in the lowest adjustable
position. The Administrator would not allow the connector to be located
on or in the center console (i.e., neither on the horizontal faces near
the floor-mounted gear selector, parking brake lever, or cup-holders,
nor on the vertical faces near the car stereo, climate system, or
navigation system controls). The location of the connector must be
easily identifiable and accessed (e.g., to connect an off-board tool).
For vehicles equipped with a driver's side door, the connector would
have to be easily identified and accessed by someone standing (or
``crouched'') on the ground outside the driver's side of the vehicle
with the driver's side door open.
If a manufacturer wants to cover the connector, the cover must be
removable by hand without the use of any tools and be labeled ``OBD''
to aid technicians in identifying the location of the connector. Access
to the diagnostic connector could not require opening or removing any
storage accessory (e.g., ashtray, coinbox). The label would have to
clearly identify that the connector is located behind the cover and is
consistent with language and/or symbols commonly used in the automobile
and/or heavy truck industry.
If the ISO 15765-4 protocol (see section II.F.3) is used for the
required OBD standardized functions, the connector would have to meet
the ``Type A'' specifications of SAE J1962. Any pins in the connector
that provide electrical power must be properly fused to protect the
integrity and usefulness of the connector for diagnostic purposes and
may not exceed 20.0 Volts DC regardless of the nominal vehicle system
or battery voltage (e.g., 12V, 24V, 42V).
If the SAE J1939 protocol (see section II.F.3)) is used for the
required OBD standardized functions, the connector must meet the
specifications of SAE J1939-13. Any pins in the connector that provide
electrical power must be properly fused to protect the integrity and
usefulness of the connector for diagnostic purposes.
Manufacturers would be allowed to equip engines/vehicles with
additional diagnostic connectors for manufacturer-specific purposes
(i.e., purposes other than the required OBD functions). However, if the
additional connector conforms to the ``Type A'' specifications of SAE
J1962 or the specifications of SAE J1939-13 and is located in the
vehicle interior near the required connector as described above, the
connector(s) must be clearly labeled to identify which connector is
used to access the standardized OBD information proposed below.

[[Page 3245]]

3. Communications to a Scan Tool
a. Background
In light-duty OBD, manufacturers are allowed to use one of four
protocols for communication between a generic scan tool and the
vehicle's onboard computer. A generic scan tool automatically cycles
through each of the allowable protocols until it hits upon the proper
one with which to establish communication with the particular onboard
computer. While this has generally worked successfully in the field,
some communication problems have arisen.
In an effort to address these problems, CARB has made recent
changes to their light-duty OBD II regulation that require all light-
duty vehicle manufacturers to use only one communication protocol by
the 2008 model year. In making these changes, CARB staff argued that
their experience with standardization under the OBD II regulation
showed that having a single set of standards used by all vehicles would
be desirable. CARB staff argued that a single protocol offers a
tremendous benefit to both scan tool designers and service technicians.
Scan tool designers could focus on added feature content and could
expend much less time and money validating basic functionality of their
product on all the various permutations of protocol interpretations
that are implemented. In turn, technicians would likely get a scan tool
that works properly on all vehicles without the need for repeated
software updates that incorporate ``work-arounds'' or other patches to
fix bugs or adapt the tool to accommodate slight variances in how the
multiple protocols interact with each other or are implemented by
various manufacturers. Further, a single protocol should also be
beneficial to fleet operators that use add-on equipment such as data
loggers, and for vehicle manufacturers that integrate parts from
various engine and component suppliers all of which must work together.
Based on our similar experiences at the federal level with
communication protocols giving rise to service and inspection/
maintenance program issues, we initially wanted to propose a single
communication protocol for engines used in over 14,000 pound vehicles.
However, the affected industry has been divided over which single
protocol should be required and has strongly argued for more than one
protocol to be allowed. Therefore, for vehicles with diesel engines, we
are proposing that manufacturers be required to use either the
standards set forth in SAE J1939, or those set forth in the 500 kbps
baud rate version of ISO 15765. For vehicles with gasoline engines, we
are proposing that manufacturers be required to use the 500 kbps baud
rate version of ISO 15765. Manufacturers would be required to use only
one standard to meet all the standardization requirements on a single
vehicle; that is, a vehicle must use only one protocol for all OBD
modules on the vehicle.
Several in the heavy-duty industry have argued for options that
would allow the use of more than these two protocols on heavy-duty
engines. Some have even argued for combinations of these protocols--
e.g., diagnostic connector and messages of ISO 15765 on an SAE J1939
physical layer network. However, as described above, experience from
multiple protocols and multiple variants within the protocols has
unnecessarily caused a significant number of problems with engine and
vehicle related computer communications.
b. Requirements for Communications to a Scan Tool
We are proposing that all OBD control modules--e.g., engine,
auxiliary emission control module--on a single vehicle be required to
use the same protocol for communication of required emissions-related
messages from onboard to off-board network communications to a scan
tool meeting SAE J1978 specifications or designed to communicate with a
SAE J1939 network. Engine manufacturers would not be allowed to alter
normal operation of the engine emissions control system due to the
presence of off-board test equipment accessing the OBD information
proposed below. The OBD system would be required to use one of the
following standardized protocols:
? ISO 15765-4 and all required emission-related messages
using this protocol would have to use a 500 kbps baud rate.
? SAE J1939 which may only be used on vehicles with diesel engines.
4. Required Emissions Related Functions
Most of the proposed emissions related functions are elements that
exist in our light-duty OBD requirements. We are proposing several
required functions, these are:
? Readiness status
? Distance and number of warm-up cycles since DTC clear
? Permanent DTC storage
? Real time indication of monitor status
? Communicating readiness status to the vehicle operator
? Diagnostic trouble codes (DTC)
? Data stream
? Freeze frame
? Test results
? Software calibration identification
? Software calibration verification number
? Vehicle identification number (VIN)
i. Readiness Status
The main intent of readiness status is to ensure that a vehicle is
ready for an OBD-based inspection--by indicating that monitors have run
and operational status of the emissions-control system has been fully
evaluated--and to prevent fraudulent testing in inspection programs. In
general, for OBD-based inspections, technicians ``fail'' a vehicle with
an illuminated MIL since this would indicate the presence of an
emissions control system malfunction. Without the readiness status
indicators, technicians would not have a clear indication from the OBD
system that it had sufficiently evaluated the emissions control system
prior to the inspection. Since the potential exists for OBD checks to
be used as part of a heavy truck inspection program, we believe that
having readiness status indicators as part of this proposal is
important--waiting for a subsequent OBD-I/M rulemaking to require such
indicators would unnecessarily delay implementation of such OBD-I/M
programs.
Absent such OBD-I/M programs, we still believe that readiness
indicators are an important OBD tool. Technicians would be expected to
use the readiness status to verify OBD-related repairs. Specifically,
technicians would clear the computer memory after repairing an OBD-
detected fault in order to erase the DTC, extinguish the MIL, and reset
the readiness status to ``incomplete.'' Then the vehicle could be
operated in such a manner that the monitor of the repaired component
would run (i.e., the readiness status of the monitor would be set to
``complete''). The absence of any DTCs or MIL illumination upon readiness
status indicating ``complete'' would indicate a successful repair.
Therefore, we are proposing that manufacturers be required to
indicate the readiness status of the OBD monitors. This would serve to
indicate whether or not engine operation has been sufficient to allow
certain OBD monitors to perform their system evaluations. The OBD
system would be required to report a readiness status of either
``complete'' if the monitor has run a sufficient number of times to
detect a malfunction since computer memory was last cleared,
``incomplete'' if the monitor has not yet run a sufficient number of
times since the memory was last cleared, or ``not applicable'' if the

[[Page 3246]]

monitor is not present or if the specific monitored component is not
equipped on the vehicle. The readiness status of monitors that are
required to run continuously would always indicate ``complete.'' The
details of the proposal discussed below clarify that the readiness
status would be set to ``incomplete'' whenever memory is cleared either
by a battery disconnect or by a scan tool but not after a normal
vehicle shutdown (i.e., key-off).
ii. Distance Traveled and Number of Warm-Up Cycles Since DTC Clear
As originally envisioned in our OBD-I/M rulemaking (61 FR 40940),
we intended to require that all readiness status indicators be set to
``complete'' prior to accepting a vehicle for I/M inspection. However,
it became clear that some vehicles were being rejected from inspection
for reasons beyond the driver's control. For example, a vehicle driven
in extreme ambient conditions would prohibit monitors from running and
setting readiness status indicators to ``complete.'' Also, a vehicle
repaired just prior to arriving at the inspection station may not have
been operated sufficiently to set the readiness status of the monitor
for the recently repaired component to ``complete.'' The driver of such
a vehicle would, in essence, be punished unintentionally for having
taken the time and expense to repair the vehicle just prior to the
inspection. As a result, we issued guidance (cite) to state inspectors
recommending that vehicles be accepted for I/M inspection provided two
or fewer readiness status indicators are ``incomplete.'' Note that most
light-duty gasoline vehicles--the bulk of the vehicle fleet facing OBD-
I/M checks--have only four monitors for which the readiness status
indicator is meaningful (all of their other monitors being continuous
monitors). However, there exists evidence that this policy is perhaps
accepting vehicles for I/M inspection that should not be accepted due
to unscrupulous clearing of DTCs and readiness status by people that
understand how to do so and then operate their vehicles just enough to
set the required minimum number of readiness indicators to ``complete.''
As a result, we are proposing some additional features that should
better differentiate between vehicles that have been repaired recently
or have ``incomplete'' readiness indicators through circumstances
outside the driver's control, and those vehicles operated by drivers
that are attempting to fraudulently get through an OBD-based
inspection. We are proposing that the OBD system make available data
that would report the distance traveled or engine run time for those
engines that do not use vehicle speed information, and the number of
warm-up cycles since the fault memory was last cleared.\46\ By
combining these data with the readiness data, technicians or inspectors
would better be able to determine if ``incomplete'' readiness status
indicators or an extinguished MIL are due to unscrupulous memory
clearing or circumstances beyond the driver's control. For example, a
vehicle with several ``incomplete'' readiness indicators but with a
high distance traveled/engine run time and a high number of warm-up
cycles since the last clearing of fault memory would be unlikely to
have undergone a recent fault memory clearing for the purpose of
extinguishing the MIL prior to inspection. On the other hand, a vehicle
with only one or two ``incomplete'' readiness indicators and a very low
distance traveled/engine run time and a low number of warm-up cycles
since fault memory clearing should probably be rejected or failed at an
inspection. This would better allow an inspection program to be set up
to reject only those vehicles with recently cleared memories while
minimizing the chances of rejecting vehicles that driven such that
monitors rarely run whether by unique driver behaviors or extreme
ambient conditions.
---------------------------------------------------------------------------

\46\ The fault memory being any DTCs, readiness status
indicators, freeze frame information, etc.
---------------------------------------------------------------------------

iii. Permanent Diagnostic Trouble Code Storage
Consistent with the proposal for distance traveled/engine run time
and number of warm-up cycles, we are proposing a requirement to make it
much more difficult for a vehicle owner or technician to clear the
fault memory and erase all traces of a previously detected malfunction.
Current OBD systems on under 14,000 pound vehicles allow a technician
or vehicle owner to erase all DTCs and extinguish the MIL by issuing a
command from a generic scan tool or, in many cases, simply by
disconnecting the vehicle battery. This would set to ``incomplete'' the
readiness status indicators for all monitors and would remove all
record of the malfunction that had been detected.
We are proposing that manufacturers be required to store in non-
volatile memory random access memory (NVRAM) a minimum of four MIL-on
DTCs that are, at present, commanding the MIL-on. These ``permanent''
DTCs would have to be stored in NVRAM at the end of every key cycle. By
requiring these permanent DTCs to be stored in NVRAM, one would not be
able to erase them simply by disconnecting the battery. Further,
manufacturers would not be allowed to design their OBD systems such
that these permanent DTCs could be erased by any generic or
manufacturer-specific scan tool command. Instead, the permanent DTCs
could be erased only via an OBD system self-clearing--i.e., upon
evaluating the component or system for which the permanent DTC has been
stored and detecting on sufficient drive cycles that the malfunction is
no longer present, the OBD system would erase the fault memory as
discussed in section II.A.2. Once this has occurred, the permanent DTC
stored in NVRAM would be erased also.
The permanent DTCs should help if states choose to implement OBD-
based I/M programs for heavy trucks. A truck with readiness status
indicators for EGR and boost control set to ``incomplete'' and with
permanent DTCs stored for both EGR and boost control would quite
probably be a truck that should be rejected from inspection. The OBD
system on such a truck has almost certainly had its fault memory
cleared--via scan tool command or battery disconnect--which would set
the readiness indicators to ``incomplete'' and erase all MIL-on DTCs
but would still have permanent DTCs stored (only the OBD system itself
can erase permanent DTCs). Likewise, a truck with the same readiness
indicators set to ``incomplete'' and no permanent DTCs for those
monitors should almost certainly be accepted for inspection since the
lack of readiness is almost certainly due to circumstances outside the
driver's control.
We believe that the permanent DTCs also provide advantages to
technicians attempting to repair a malfunction and prepare it for
subsequent inspection or proof of correction. The permanent DTC would
identify the specific monitor that would need to be exercised after
repair and prior to inspection to be sure that the malfunction has been
repaired. By combining this information with the vehicle manufacturer's
service information, technicians could identify the exact conditions
necessary to exercise the particular monitor. As such, technicians
could more effectively verify that the specific monitor (that monitor
having illuminated the MIL for which the repair has been done) has run
and confirmed that the malfunction no longer exists and the repair has
been made correctly. This should also reduce vehicle owner ``come-
backs'' for incomplete or ineffective repairs.

[[Page 3247]]

iv. Real Time Indication of Monitor Status
We are also proposing provisions to make it easier for technicians
to prepare a vehicle for an inspection following a repair. These
provisions would require that the OBD system provide real time data
that indicate whether the necessary conditions are present currently to
set all of the readiness indicators to ``complete.'' These data would
indicate whether a particular monitor may still have an opportunity to
run on the current drive cycle or whether a condition has been
encountered that has disabled the monitor for the rest of the drive
cycle regardless of the driving conditions that might be encountered.
While these data would not provide technicians with the exact
conditions necessary to exercise the monitors (only service information
would provide such information), the date in combination with the
service information should assist technicians in verifying repairs and/
or preparing a vehicle for inspection. Technicians would be able to use
this information to identify when specific monitors have indeed
completed or to identify situations where they have overlooked one or
more of the enable criteria and need to check the service information
and try again.
v. Communicating Readiness Status to the Vehicle Operator
As mentioned above, substantial feedback has been received from
OBD-based I/M programs throughout the U.S. Much of this feedback
pertains to the effect on vehicle owners caused by being rejected from
I/M inspection due to ``incomplete'' readiness status indicators. To
address this, some light-duty vehicle manufacturers requested that they
be allowed to communicate the vehicle's readiness status to the vehicle
owner directly without need of a scan tool. This would provide
assurance to the vehicle owner that their vehicle is ready for
inspection prior to taking the vehicle to the I/M station. We are
proposing that heavy-duty engine manufacturers be allowed to do the
same thing (this is a proposed option, not a proposed requirement). If
a manufacturer chooses to implement this option, though, they would be
required to do so in a standardized manner. On engines equipped with
this option, the owner would be able to initiate a self-check of the
readiness status, thereby greatly reducing the possibility of being
rejected at a roadside inspection.
vi. Diagnostic Trouble Codes (DTC)
Malfunctions are reported by the OBD system and displayed on a scan
tool for service technicians in the form of diagnostic trouble codes
(DTCs). We are proposing that manufacturers be required to report all
emissions-related DTCs using a standardized format and to make them
accessible to all service technicians, including the independent
service industry. The reference document standards selected by the
manufacturer would define many generic DTCs to be used by all
manufacturers. In the rare circumstances that a manufacturer cannot
find within the reference documents a suitable DTC, a unique
``manufacturer-specific'' DTC could be used. However, such
manufacturer-specific DTCs are not as easily interpreted by the
independent service industry. Excessive use of manufacturer-specific
DTCs may increase the time and cost for vehicle repairs. Thus, we are
proposing to restrict the use of manufacturer-specific DTCs. If a
generic DTC suitable for a given malfunction cannot be found, the
manufacturer would be expected to pursue approval and addition of
appropriate generic DTCs into the reference documents; the intent being
to standardize as much information as possible.
Additionally, we are proposing that the OBD system store DTCs that
are as specific as possible to identify the nature of the malfunction.
The intent being to provide service technicians with as detailed
information as possible to diagnose and repair vehicles in an efficient
manner. In other words, manufacturers should use separate DTCs for
every monitor where the monitor and repair procedure, or likely cause
of the failure, is different. Generally, a manufacturer would design an
OBD monitor that detects different root causes (e.g., sensor shorted to
ground or battery) for a malfunctioning component or system. We would
expect manufacturers to store a specific DTC such as ``sensor circuit
high input'' or ``sensor circuit low input'' rather than a general code
such as ``sensor circuit malfunction.'' Further, we expect
manufacturers to store different DTCs that distinguish circuit
malfunctions from rationality and functional malfunctions since the
root cause for each is different and, thus, the repair procedures may
be different.
We are also proposing specific provisions for storage of pending
and MIL-on DTCs. These proposed provisions were discussed in section
II.A.2.
We are also proposing requirements that would help to distinguish
between DTCs stored for malfunctions that are currently present and for
malfunctions that are no longer present. These requirements would apply
only to those engines using ISO 15765-4 as the communication protocol.
As described in section II.A.2, the OBD system would generally
extinguish the MIL if the malfunction responsible for the MIL
illumination has not been detected (i.e., the monitor runs and
determines that the malfunction no longer exists) on three subsequent
sequential drive cycles. However, a manufacturer would not be allowed
to erase the associated MIL-on DTC until 40 engine warm-up cycles have
occurred without again detecting the malfunction. So even though the
malfunction is no longer present and a MIL-on is not being commanded,
the DTC would still remain (termed a ``history'' code in the ISO
standard). Consequently, if another unrelated malfunction occurs and
results in a MIL-on, a new DTC would be stored along with the history
DTC. When trying to diagnose the OBD problem, technicians accessing DTC
information may have trouble distinguishing which DTC is responsible
for illuminating the MIL (i.e., which malfunction is present
currently), and thus could have trouble determining what exactly must
be repaired. Therefore, we are proposing this requirement for ISO
engines to help distinguish between DTCs stored for malfunctions that
are present and those that were present. Note that, for engines using
SAE J1939 as the communication protocol, such a distinction is already
provided for.
Permanent DTCs would also need to be separately identified from the
other types of DTCs. Additionally, as described above, manufacturers
would be required to develop additional software routines to store and
erase permanent DTCs in NVRAM and to prevent erasure from any battery
disconnect or scan tool command.
vii. Data Stream/Freeze Frame/Test Results
An important aspect of OBD is the ability of technicians to access
critical information from the onboard computer to diagnose and repair
emissions-related malfunctions. We believe that having access through
the diagnostic connector to real-time electronic information regarding
certain emissions critical components and systems would provide
valuable assistance for repairing vehicles properly. The availability
of real-time information would also provide assistance to technicians

[[Page 3248]]

responding to drivability complaints since the vehicle could be
operated within the necessary operating conditions and the technician
could see how various sensors and systems were acting. Similarly, fuel
economy complaints, loss of performance complaints, intermittent
problems, and others issues could also be addressed.
We are proposing a number of data parameters that the OBD system
would be required to report to a generic scan tool. These parameters,
which would include information such as engine speed and exhaust gas
sensor readings, would allow technicians to understand how the vehicle
engine control system is functioning, either as the vehicle operates in
a service bay or during actual driving. They would also help
technicians diagnose and repair emission-related malfunctions by
allowing them to watch instantaneous changes in the values while
operating the vehicle.
Some of the data parameters we are proposing are intended to assist
us in performing in-use testing of heavy-duty engines for compliance
with emissions standards. One of the parameters that manufacturers
would be required to report is the real-time status of the
NO_X and PM ``not-to-exceed'' (NTE) control areas. The NTE
standards define a wide range of engine operating points where a
manufacturer must design the engine to be below a maximum emission
level. In theory, whenever the engine is operated within the speed and
load region defined as the NTE zone, emissions will be below the
required standards. However, within the NTE zone, manufacturers are
allowed, if justified on a case-by-case basis, to either modify the
time frame in which the standard must be met, and in the second case to
be exempted from the emission standards under specific conditions
(e.g., an NTE deficiency). Manufacturers can request two types of
modifications: first, a five percent limited testing region within
which no more than five percent of in-use operation is expected to
occur and, thus, no more than five percent of NTE emissions sampling
within that region can be compared to the NTE standard for a given
sampling event; and second, NTE deficiencies which are precisely
defined exemption conditions where compliance cannot be met due to
technical reasons or for engine protection. These regions and
conditions can be defined by directly measured signals or, in some
cases, by complicated modeled values calculated internally in the
engine computer. When conducting emissions testing of these engines,
knowing if the engine is inside the NTE zone--and subject to the NTE
standards--or is outside of the NTE zone or, perhaps, in an NTE limited
testing region or covered by an NTE deficiency is imperative. As our
in-use testing program requirements are written currently, we must post
process data to determine which data points were generated within a
compliance zone and which were generated within an exempted zone. Such
post processing, while possible, is inefficient, time consuming, and
resource intensive. Having the NTE zone data broadcast in real-time
over the engine's network would allow for a much more efficient use of
our resources.
The specific parameters we are proposing for inclusion in the data
stream are, for gasoline engines: calculated load value, engine coolant
temperature, engine speed, vehicle speed, time elapsed since engine
start, absolute load, fuel level (if used to enable or disable any
other monitors), barometric pressure (directly measured or estimated),
engine control module system voltage, commanded equivalence ratio,
number of stored MIL-on DTCs, catalyst temperature (if directly
measured or estimated for purposes of enabling the catalyst
monitor(s)), monitor status (i.e., disabled for the rest of this drive
cycle, complete this drive cycle, or not complete this drive cycle)
since last engine shut-off for each monitor used for readiness status,
distance traveled/engine run time with a commanded MIL-on, distance
traveled/engine run time since fault memory last cleared, number of
warm-up cycles since fault memory last cleared, OBD requirements to
which the engine is certified (e.g., California OBD, EPA OBD, non-OBD)
and MIL status (i.e., commanded-on or commanded-off). And, for diesel
engines: calculated load (engine torque as a percentage of maximum
torque available at the current engine speed),\47\ driver's demand
engine torque (as a percentage of maximum engine torque), actual engine
torque (as a percentage of maximum engine torque), reference engine
maximum torque, reference maximum engine torque as a function of engine
speed (suspect parameter numbers (SPN) 539 through 543 defined in SAE
J1939 within parameter group number (PGN) 65251 for engine
configuration), engine coolant temperature, engine oil temperature (if
used for emission control or any OBD monitors), engine speed, time
elapsed since engine start, fuel level (if used to enable or disable
any other diagnostics), vehicle speed (if used for emission control or
any OBD monitors), barometric pressure (directly measured or
estimated), engine control module system voltage, number of stored MIL-
on DTCs, monitor status (i.e., disabled for the rest of this drive
cycle, complete this drive cycle, or not complete this drive cycle)
since last engine shut-off for each monitor used for readiness status,
distance traveled/engine run time with a commanded MIL-on, distance
traveled/engine run time since fault memory last cleared, number of
warm-up cycles since DTC memory last cleared, OBD requirements to which
the engine is certified (e.g., EPA OBD parent rating, EPA OBD child
rating, non-OBD), and MIL status (i.e., commanded-on or commanded-off).
Also for diesel engines, as discussed above, separate NO_X
and PM NTE control area status (i.e., inside control area, outside
control area, inside manufacturer-specific NTE carve-out area, or
deficiency active area). Also, for all engines so equipped (and only
those so equipped): absolute throttle position, relative throttle
position, fuel control system status (e.g., open loop, closed loop),
fuel trim, fuel pressure, ignition timing advance, fuel injection
timing, intake air/manifold temperature, engine intercooler
(aftercooler) temperature, manifold absolute pressure, air flow rate
from mass air flow sensor, secondary air status (upstream, downstream,
or atmosphere), ambient air temperature, commanded purge valve duty
cycle/position, commanded EGR valve duty cycle/position, actual EGR
valve duty cycle/position, EGR error between actual and commanded, PTO
status (active or not active), redundant absolute throttle position
(for electronic throttle or other systems that utilize two or more
sensors), absolute pedal position, redundant absolute pedal position,
commanded throttle motor position, fuel rate, boost pressure,
commanded/target boost pressure, turbo inlet air temperature, fuel rail
pressure, commanded fuel rail pressure, DPF inlet pressure, DPF inlet
temperature, DPF outlet pressure, DPF outlet temperature, DPF delta
pressure, exhaust pressure sensor output, exhaust gas temperature
sensor output, injection control pressure, commanded injection control
pressure, turbocharger/turbine speed,

[[Continued on page 3249]]

Notices For
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2002
2001
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1996
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