MALFUNCTION INDICATOR LIGHT (MIL)
Vehicle is equipped with a Malfunction Indicator Light (MIL). As a bulb check, the MIL will illuminate for about 5 seconds whenever ignition is turned on. The MIL will also illuminate when a system failure is detected; a corresponding Diagnostic Trouble Code (DTC) will set in Electronic Control Module (ECM) memory.
The ECM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, the ECM will illuminate the MIL (CHECK ENGINE light) on instrument panel. When a malfunction is detected and the MIL is illuminated, a corresponding DTC will be stored in the ECM. To retrieve DTCs, see RETRIEVING DTC(S) . Malfunctions are recorded as hard failures or as intermittent failures.
Hard Failures
Hard failures cause the MIL to come on and remain on until the problem is repaired. If the MIL comes on and remains on during vehicle operation, retrieve DTC(s). See RETRIEVING DTC(S) .
Intermittent Failures
Intermittent failures may cause the MIL to flicker on, and off after the intermittent fault goes away. The corresponding DTC will be retained in ECM memory. If the related fault does not reoccur within a certain time frame, the related DTC may be erased from memory. Intermittent failures may be caused by sensor, connector, or wiring problems. See INTERMITTENTS in TESTS W/O CODES article.
ECM POWER & GROUND CIRCUITS
See SYSTEM/COMPONENT TESTS article.
SUMMARY
If no hard fault codes (or only pass codes) exist, driveability symptoms exist, or intermittent codes exist, go to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.
NO MALFUNCTION INDICATOR LIGHT (MIL)
Turn ignition on, with engine off. If MIL does not illuminate, inspect bulb. Replace bulb if faulty. If bulb is okay, check for open in circuit or a faulty fuse.