Using MIL
Malfunction Indicator Light (MIL) can be used for DTC retrieval and front Heated Oxygen Sensor (HO2S) monitoring. See Fig 1. When ignition is turned on with engine off, MIL should illuminate. This is a bulb check. If MIL does not illuminate, repair MIL circuit. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. When engine is started, MIL should go off. If MIL remains on, ECM has detected a malfunction. If MIL is flashing when engine is running, ECM may be in diagnostic test mode II.