Vehicle Emissions Inspection and Maintenance (I/M): Information for State and Local I/M Agencies
On this page
- General Information
- Policy and Technical Guidance
- On-Board Diagnostic (OBD) Resources
- Auditing Resources
- Additional Technical Resources
Vehicle inspection and maintenance (I/M) programs help improve air quality by identifying cars and trucks with high emissions and that may need repairs. Owners or operators of vehicles with high emissions are notified to make any repairs so that emissions are within legal limits. The 1990 Amendments to the Clean Air Act (CAA) established I/M requirements for several areas across the country. This page contains useful resources for State and Local jurisdictions operating Vehicle I/M programs.
- Overview of Vehicle Inspection and Maintenance (I/M) Programs (pdf) (EPA-420-F-21-067, October 2021)
This document provides information on I/M programs such as where I/M programs are required and an overview of I/M testing.
- OBD Clearinghouse: Weber State University's Center for Automotive Science and Technology
Learn the latest on state and local OBD I/M implementation, technician training opportunities and state outreach materials.
EPA has developed policy and technical guidance on several topics related to I/M program implementation, annual reporting, performance standard modeling, biennial program evaluation, and more that may be relevant for State and Local I/M Agencies available on the Vehicle Emissions Inspection and Maintenance (I/M): Policy and Technical Guidance page.
- OBD Readiness Testability Issues (pdf) (EPA-420-B-12-044, June 2012)
This memo and accompanying document update the I/M OBD Vehicles Readiness Exception List (pdf) (EPA420-F-08-009, January 2008) to list specific vehicle makes and models with OBD readiness issues and make suggestions for how I/M programs can improve operational performance by addressing monitor readiness.
- On-Board Diagnostics (OBD) Inspection and Maintenance (I/M) Program Implementation for Flexible Fuel Vehicles (FFVs) (pdf) (EPA-420-B-07-022, May 2007)
This document is to provide additional information on the inspection process of alternative fueled vehicles equipped with On-Board Diagnostic (OBD) systems. Specifically, this document provides additional technical information and impacts on the OBD system monitoring capability when flexible fuel vehicles (FFVs) are operated using alternative fuel.
- EPA Steady State and Transient Testing Equipment Audit Guidelines (July 2001)
These guidelines should be used by states as a comprehensive tool for auditing I/M tailpipe testing equipment. The below forms are to be used with these guidelines.
- Audit Forms (July 2001)
- Memorandum of Exemption for Investigations (Covert Audits) (pdf) (EPA420-B-99-010, December 1999)
This form provides that the appropriate state enforcement divisions within the state or local government, which have jurisdiction over the I/M covert audit program, the authority to conduct covert audits upon acknowledging the terms and conditions of this memorandum of exemption. Instructions for submitting requests for exemption and contact information are available within the linked form above.
- Remote Sensing: A Supplemental Tool for Vehicle Emission Control (pdf) (EPA400-F-92-017, August 1993)
A fact sheet looking at the role of remote sensing as a tool to evaluate vehicle emissions.
- The IM240 Transient I/M Dynamometer Driving Schedule and The Composite I/M Test Procedure (pdf) (EPA-AA-TSS-91-1, January 1991)
This document provides descriptive information about the IM240 driving schedule test and provides information on EPA’s Composite I/M Test Procedure (CITP).