About OBD Codes

OBD Codes explains the fault codes that a car's computer stores when the check engine light comes on. It covers 450 generic OBD-II codes in 57 groups, in plain language: what the code means, what you may notice, the usual causes, how serious it is and what to check first. A decoder on the home page explains the structure of any code.

Where the content comes from

The numbering of generic OBD-II codes is set by international standards (SAE J2012 and ISO 15031-6), and is the same for every make of car. The explanations on this site are written by us in our own words, from general knowledge of how these systems work. We do not copy the text of the standards or of any repair manual. Written in November 2026.

What this site does not cover

• Maker-specific codes (such as P1xxx). Each car maker gives these its own meaning, so we only explain how to recognise them.
• Repair instructions for your model. Test steps, part locations and torque values differ from car to car and belong in the workshop manual.
• Body and chassis codes in detail (B and C codes). Their use varies too much between makers.

Please read

A code points to a system, not to a failed part. Always have a qualified mechanic confirm the cause before spending money on parts. Work on fuel systems, airbags, brakes and high-voltage hybrid parts can injure or kill and must be left to trained people.

Who makes it

This site is part of ShareYourGroup, a family of free sites about the things people share, send and do together. It is free to use and needs no login. Advertisements pay for the hosting and the work.

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