Malfunction Indicator Light
The ECM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction that may affect vehicle emissions is detected during 2 sequential drive cycles, the ECM will illuminate the MIL on the instrument panel. See Fig 1. A corresponding DTC will be stored in ECM memory. If a misfire is detected, MIL will illuminate and DTC will be stored in ECM immediately after fault is detected. If misfire is severe enough to cause catalytic converter damage, MIL will blink. MIL will continuously blink until danger to catalytic converter has passed. To retrieve stored DTC(s). See RETRIEVING DIAGNOSTIC TROUBLE CODES .
If battery is disconnected, all DTCs and freeze frame data will be erased from ECM. As a bulb check, MIL will also illuminate for about 5 seconds when ignition is turned on.