What does it mean when the OBD light on the car is on?

[OJack]

The reason why the OBD light on the car is on is: the vehicle has an emission fault. The illuminated OBD light indicates that the vehicle's exhaust components severely exceed standards, serving as the engine exhaust system fault indicator. OBD stands for On-Board Diagnostics in Chinese, and this system continuously monitors the engine's operating conditions and the working status of the exhaust after-treatment system. It immediately issues a warning upon detecting any condition that may cause emissions to exceed standards. When a fault occurs in the OBD system, the Malfunction Indicator Lamp (MIL) or Check Engine warning light illuminates. Simultaneously, the Powertrain Control Module (PCM) stores the fault information in memory, and the fault code can be read from the PCM through a specific procedure. Based on the fault code's indication, maintenance personnel can quickly and accurately determine the nature and location of the fault.