OBD2 Fault Codes Library

Find the exact definition, driving safety level, symptoms, and potential repairs for your vehicle's check engine light codes.

What are OBD-II Diagnostic Trouble Codes (DTCs)?

Diagnostic Trouble Codes (DTCs) are codes generated by your car's onboard computer system (OBD) when it detects a sensor reading outside normal parameters. The system was standardized in 1996 to enable rapid identification of vehicle malfunctions. The letters in the code categorize the system: P stands for Powertrain (Engine & Transmission), C for Chassis (Brakes & Steering), B for Body (Climate, Airbags, Lights), and U for Network communications (CAN bus & ECUs).

Powertrain (P) Codes