Car OBD Codes

OBD-II (On-Board Diagnostics II) codes are standardized diagnostic trouble codes (DTCs) used by all vehicles manufactured after 1996. When your car's check engine light comes on, an OBD-II scanner can read these codes to identify the specific issue with your vehicle.

Each code follows a standard format: a letter followed by four digits. The first letter indicates the system — P for Powertrain (engine, transmission), B for Body (airbags, A/C, lighting), C for Chassis (ABS, brakes, steering), and U for Network communication (CAN bus, modules).

The second character indicates whether the code is a generic/standard code (0, 2, 3) defined by the SAE, or a manufacturer-specific code (1) unique to the vehicle maker. Generic codes are the same across all makes — a P0300 means the same thing whether you drive a Toyota, Ford, BMW, or Honda.

To read OBD-II codes from your vehicle, you need an OBD-II scanner (also called a code reader). Plug it into the OBD-II port, usually located under the dashboard near the steering column. The scanner will display any stored diagnostic trouble codes.

Once you have the code (e.g., P0300, P0171, B1200), search for it on this site to find the meaning, common symptoms, likely causes, and possible fixes. This can help you understand the issue before visiting a mechanic, potentially saving time and money on diagnosis.