What does OBD mean for cars?

[StClaire]

OBD for cars refers to the On-Board Diagnostics system, which continuously monitors the engine's operating conditions to check if the vehicle's emissions exceed standards. If they do, it will immediately issue a warning. The functions of the On-Board Diagnostics system include: automatically monitoring the engine's operating status and diagnosing the working conditions of other components in the car. When a fault occurs in any system of the car, the fault light will trigger an alert. The OBD device can simultaneously detect multiple systems and components in the car, mainly including: the engine, catalytic converter, particulate filter, oxygen sensor, emission control system, and fuel system.