Onboard diagnostics (OBD) is an automotive term referring to a vehicle’s self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the various vehicle subsystems.
The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of onboard vehicle computers. Earlier versions of OBD would illuminate a malfunction indicator light or “idiot light” if a problem was detected but would not provide any information as to the nature of the problem.
Modern OBD implementations use a standardized digital communications port to provide real-time data and a standardized series of diagnostic trouble codes, or DTCs, allowing one to identify and remedy malfunctions within the vehicle rapidly.