OBD-II

On-board diagnostics, second generation, became mandatory for new cars in the USA in 1996. Europe introduced the equivalent EOBD for petrol cars from 2001 and diesels from 2004. It standardises the diagnostic socket, the communication protocols and the generic fault codes defined in SAE J2012.

Every compliant car has a 16-pin socket, usually under the dashboard near the steering column. Any generic scan tool can read engine codes, freeze frame data and live values through it. OBD-II has been mandatory in the United States since model year 1996. Europe introduced the comparable EOBD for petrol cars from 2001 and diesel cars from 2004.

The control unit runs monitors for misfire, catalyst, oxygen sensors, EVAP, EGR and more. When a fault is confirmed, it stores a code and switches on the engine warning light (MIL). The 16-pin diagnostic connector, usually under the dashboard, gives access to fault codes, live data and readiness monitors.

OBD-II codes are the starting point for most engine diagnosis. Generic codes (P0xxx, P2xxx) mean the same on every car; manufacturer codes (P1xxx) are specific to each make. Basic OBD-II scan tools are inexpensive and can read and clear emission codes. Manufacturer-specific codes and other systems such as ABS and airbags often need more advanced tools.