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On-Board Diagnostics, or "OBD," is a computer-based system built into all 1996 and later light-duty vehicles and trucks, as required by the Clean Air Act Amendments of 1990. OBD systems are designed to monitor the performance of some of an engine's major components including those responsible for controlling emissions.

OBD impacts many audiences for different reasons.

This page is maintained by EPA's Office of Transportation and Air Quality (OTAQ).
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