CodelampCheck engine code lookup
Type your codes. See what each one means in plain words.
General information, not a mechanic's diagnosis: have a mechanic confirm before any repair.
Code pages
Each page gives the code's meaning, its likely causes from most to least common, what you can note yourself and what to tell the shop.
Common codes
Two codes together
- P0171 + P0174 both sides of the engine are lean
- P0300 + P0302 misfires, worst in cylinder 2
- P0171 + P0300 lean, and misfiring
- P0420 + P0430 both converters tested weak
- P0442 + P0455 a small and a large fuel vapor leak
- P0101 + P0171 the airflow sensor and a lean mixture
- P0133 + P0171 a slow oxygen sensor and a lean mixture
- P0420 + P0141 the converter test and its sensor
Came back after a repair
- P0420 P0420 came back after a new catalytic converter
- P0420 P0420 came back after a new oxygen sensor
- P0171 P0171 came back after cleaning the airflow sensor
- P0171 P0171 came back after a new oxygen sensor
- P0300 P0300 came back after new spark plugs
- P0300 P0300 came back after new ignition coils
- P0455 P0455 came back after a new gas cap
- P0442 P0442 came back after a new gas cap
How it works
Since 1996, cars sold in the US report engine faults as standard codes. A code starting with P0 has the same meaning on every make; one starting with P1 is the maker's own. The box looks each code up in a list of common generic codes, names the system it belongs to, and says when two codes often share a cause.
A code says which test failed, not which part is broken. The causes on each page are the usual ones, in the order they are usually found, so you can ask the shop good questions before you pay for parts.
The codes you type are looked up in your browser and are not saved.