Plug an OBD-II scanner into the diagnostic port under your dashboard, turn the ignition on, and read the stored codes from the scanner screen. Many auto parts stores will read your codes for free if you do not own a scanner. Once you have the code, use the Code Lookup tool to open its guide.

New code guides are published on a regular schedule, so check back soon. Double-check that you typed the code exactly as your scanner shows it, because one wrong digit points to a different guide. You can also use the search box at the top of the site to look for your code.

These are generic OBD-II powertrain codes, so the same code means the same thing on any 1996 or newer car or light truck that uses OBD-II. Manufacturers can add their own extra codes on top of these, and those are covered in separate guides where they exist.

The letter P stands for powertrain, which covers the engine, transmission, and related emissions systems. The digits that follow point to the general area of the fault, such as misfires, fuel trim, or catalyst efficiency. Each guide on this site explains the exact meaning, symptoms, causes, and fixes for its code.

Start with the code from your scanner, then open its guide from the index above. Follow the diagnosis steps in order before replacing any parts, because the code tells you which system reported a fault, not which part to buy.