OBD2 fault code reference
Plain-English explanations for 37 of the codes drivers actually see — what each one means, what usually causes it, and whether it's safe to keep driving.
Ask the free AI helperEngine & fuel system
- P0010VVT solenoid circuit (intake, bank 1)Fix soon
- P0011VVT timing over-advanced (bank 1)Fix soon
- P0016Crank/cam correlationFix soon
- P0030Front O2 sensor heater circuitFix soon
- P0101Mass airflow sensor — out of rangeWatch
- P0102MAF circuit low inputFix soon
- P0113IAT sensor circuit highWatch
- P0128Coolant below thermostat regulating tempWatch
- P0171System too lean (bank 1)Fix soon
- P0172System too rich (bank 1)Fix soon
- P0174System too lean (bank 2)Fix soon
- P0300Random/multiple cylinder misfireFix soon
- P0301Cylinder 1 misfireFix soon
- P0302Cylinder 2 misfireFix soon
- P0303Cylinder 3 misfireFix soon
- P0304Cylinder 4 misfireFix soon
- P0305Cylinder 5 misfireFix soon
- P0306Cylinder 6 misfireFix soon
- P0420Catalyst efficiency below threshold (bank 1)Watch
- P0430Catalyst efficiency below threshold (bank 2)Watch
- P0507Idle speed higher than expectedWatch
Transmission
Brakes & stability
Network & modules
Evaporative emissions
These explanations are from a curated DTC knowledge base. Manufacturer-specific codes may need a specialist's hands-on read.