OBD-II Trouble Codes Database
Browse 12139+ diagnostic trouble codes with definitions from SAE J2012, real NHTSA complaint data, and community reports.
What this database helps with
Use the generic code guide when you know the exact DTC, then move into vehicle pages if complaint patterns or repair history point to a known make-model path.
Best first diagnostic move
Match the code meaning first, then compare symptoms, freeze-frame data, and the most likely root-cause path before replacing parts.
What makes these guides stronger
Priority code pages combine SAE definitions, NHTSA complaint context, and reviewed diagnostic packaging so high-volume searches land on more useful answers.
Featured diagnostic guides
High-intent OBD pages with reviewed packaging and strong next-step guidance.
P0171: System Too Lean Bank 1. Reported on 34 vehicles. Most common on CHEVROLET CRUZE.
P0420 means catalyst efficiency is below threshold on Bank 1. Diagnose catalytic converter efficiency, rear O2 data, misfire, and fuel-trim causes before replacing parts.
P0300: Random/Multiple Cylinder Misfire Detected. Reported on 60 vehicles. Most common on FORD ESCAPE.
P0455: EVAP System Leak Detected - Large Leak. Reported on 23 vehicles. Most common on FORD FUSION.
Search all 12139 codes, or browse a prefix below.
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