Malfunction Indicator Lamp: Testing and Inspection

The malfunction indicator light will come on when the Electronic Control Module (ECM) detects an irregularity in one or more of the following monitored circuits: the ECM, injector, fuel pump, or in the oxygen, air flow, intake air temperature, throttle position, engine coolant temperature, crank angle, top dead center or barometric pressure sensor circuits.

When an irregular signal returns to normal or is repaired and the ECM judges that it has returned to normal, the malfunction indicator light will turn OFF. When the ignition switch is turned OFF then malfunction indicator light will turn off until such time as the irregular signal is detected again. The ECM will set and retain a fault code corresponding to the detected irregularity for 50-100 starts after the irregularity was detected unless the battery or ECM is disconnected.