Working Paper

Improving emission standards compliance with a defect reporting system for in-use passenger vehicles

An emission control defect reporting program is used in California to improve compliance with passenger vehicle emission standards. The defect reporting program was adopted by the California Air Resources Board (CARB) through regulation. The regulation requires the manufacturer of the passenger vehicles to report to CARB how many warranty claims (as a percent) for emission control parts it receives within the warranty period for the vehicle. An excessive percentage of reported warranty claims for a specific emission control part suggests there is a defect in the part that is causing or will lead to increased emissions.

Based on the defect reports, CARB may seek voluntary agreement with the vehicle manufacturer to recall the affected vehicles and replace the defective emission control part with one of an improved design. This prevents future failure of the part and thus reduces in-use emissions. Basing the recall (or other corrective action such as an extended warranty) on defect reporting can avoid costly test vehicle procurement and emission testing to demonstrate an emission standard has been exceeded, which otherwise would be a prerequisite to a recall. CARB may also use the defect reports to prioritize models for emission testing in its separate, state-run in-use compliance testing program. In either case the defect reporting system complements and increases the efficiency of CARB’s overall in-use compliance program. The U.S. Environmental Protection Agency has a similar program, which applies to vehicles sold in states not subject to CARB’s requirements. 

Vehicle testing