Diagnostic reference

Engine Code Lookup

Every OBD-II diagnostic trouble code, translated into plain English by ASE-certified techs. See severity, likely causes, and whether it's safe to keep driving — with a booking shortcut when it isn't.

Check engine light on?

Look up your engine code

Read the code with any OBD-II scanner (or ask AutoZone/O'Reilly to pull it free). Type it below to see what it means and whether you can keep driving.

Popular:P0420 P0300 P0171 P0455 P0128

Browse the library

Filter by system or search a keyword.

No codes match your search.

Try a code like P0420 above — even codes we haven't cached yet get an instant AI-generated explanation.

Know before you drive

Every code tells you whether it's safe to keep driving or you should pull over.

Likely causes ranked

See what typically triggers the code and how a real shop diagnoses it.

No guesswork on repairs

Book a diagnostic with our team — flat-rate, transparent, no surprise upsells.