A program designed to periodically check vehicle emissions to ensure they are within limits. Often referred to as an I/M (Inspection/Maintenance) program, they are used in numerous states and areas as required by the Environmental Protection Agency to improve air quality in those areas.

Although I/M requirement come from the federal government, states and their associated agencies have some flexibility in the type of test used, vehicle populations to be tested and other program-specific details. Some states run centralized programs that have state-contracted test stations exclusively dedicated to testing. Other states run decentralized programs, where emissions can be tested at local repair facilities. In a few cases, states may run "hybrid" programs using both centralized and decentralized test stations. The latest trend is to incorporate the use of second-generation onboard diagnostics (OBDII) into these programs, in many cases altogether eliminating the need for tailpipe emissions tests.

Purpose: I/M programs evaluate the emissions from vehicles and single out those that are polluting beyond the limits established for certain model years of vehicles. Aside from identifying vehicles with high emissions, such programs advocate proper maintenance to prevent high emissions due to maintenance neglect.

Maintenance Tips/Suggestions: The best way to keep your vehicle environmentally friendly is by performing regularly scheduled maintenance, rather than waiting to correct a problem after your car fails an emissions test. If the SERVICE ENGINE SOON or CHECK ENGINE light appears, have it checked out immediately by a professional technician. Neglecting these warning signs can lead to more extensive and expensive repairs.