OBD CodesWhere to start
If a warning light has just come on, read the guide to the check engine light first. It tells you the one thing that matters in the first minute: whether it is safe to keep driving. A steady light usually means the car can be driven gently to a workshop. A flashing light means stop as soon as it is safe. Once that is settled, the guide on how to read a code shows that the five characters are not random: each one narrows down where the fault lies.
If you want to read the code yourself
Every car with OBD-II has a socket, usually under the dashboard near the steering column, where a scan tool plugs in. The guides explain where to look for the socket, what an inexpensive reader can and cannot tell you, and why clearing a code does not repair anything: the car simply sets the code again when it next sees the same fault.
What a code is, and is not
A fault code says which circuit or system the car's computer is unhappy about. It does not name the part to replace. The same code can come from a failed sensor, a broken wire, a loose connector, an air leak or a worn mechanical part, and a mechanic tests to find out which. Use these guides to understand the conversation at the workshop and to avoid paying for parts that were never faulty. For any fault that affects brakes, steering, airbags or the way the engine runs, have the car checked by a qualified mechanic.