OBD CodesHave a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.
How to use this site
- Read the code with a scan tool, or ask a workshop to read it. Write down every code, not only the first.
- Type each code above. Read what it means and how serious it is.
- Do the simple checks listed, such as the fuel cap, fluid levels and loose plugs.
- Take the car and the codes to a mechanic for testing.
New to this? Start with how to read a code and what the check engine light means.
Questions
What is an OBD-II code?
It is a five-character code, such as P0420, that the car's computer stores when it detects a fault. A scan tool plugged into the diagnostic socket reads it. The code tells you which system has a problem.
Can I keep driving with the check engine light on?
If the light is steady and the car drives normally, you can usually drive carefully to a workshop. If the light is flashing, or the car shakes, loses power, overheats or shows a red warning, stop as soon as it is safe.
Does a code tell me which part to replace?
No. A code says what the computer noticed, for example that the mixture is too lean. Several different faults can cause the same code. A mechanic has to test the car to find the real cause.
Are the codes the same for every car?
Generic codes, which have 0 as the second character (such as P0171), mean the same on every make. Codes with 1 as the second character (such as P1456) are set by each car maker and differ between brands.