About DTCReader

DTCReader is a free, ad-free reference tool for automotive diagnostic trouble codes (DTCs). Whether you've just seen a check-engine light or you're a professional technician, DTCReader helps you quickly look up what a fault code means and understand how severe it is.

What it covers

DTCReader includes thousands of codes across the full OBD-II standard (P, C, B, and U codes) as well as manufacturer-specific codes for major brands including VAG Group, BMW, Mercedes-Benz, Ford, GM, Toyota, Honda, Nissan, Hyundai/Kia, Stellantis, Volvo, Jaguar Land Rover, Renault, and more.

How it works

Use the search bar to enter a code (e.g. P0420) or a keyword (e.g. catalytic converter). You can also browse by manufacturer to see brand-specific codes. Each code page shows the code, system, a plain-English description, and a severity indicator.

Disclaimer

All information on DTCReader is provided for educational and informational purposes only. A stored fault code is a starting point for diagnosis — not a definitive verdict on what part needs replacing. Always consult a qualified mechanic before making repairs. DTCReader accepts no liability for actions taken based on the information provided.