Malfunction Indicator Lamp (MIL)

Malfunction Indicator Lamp (MIL) Schematic:

The Malfunction Indicator Lamp (MIL) alerts the driver that the Powertrain Control Module (PCM) has detected an OBD II emission-related component or system fault. When this occurs, an OBD II Diagnostic Trouble Code (DTC) will be set.
- The MIL is located on the instrument cluster and is labeled CHECK ENGINE or SERVICE ENGINE SOON.
- Power is supplied to the MIL whenever the ignition switch is in the RUN or START position.
- The MIL will remain on in the RUN/START mode as a bulb check during the instrument cluster proveout for approximately 4 seconds.
- If the MIL remains ON after the bulb check:
- The PCM illuminates the MIL for an emission related concern and a DTC will be present.
- The instrument cluster will illuminate the MIL if the PCM does not send a control message to the instrument cluster.
- The PCM is operating in the Hardware Limited Operation Strategy (HLOS).
- The MIL circuit is shorted to ground.
- If the MIL remains OFF (during the bulb check):
- Bulb is damaged.
- MIL circuit is open.
- To turn off the MIL after a repair, a reset command from the Scan Tool must be sent, or three consecutive drive cycles must be completed without a fault.
- For any MIL concern, go to Symptom Charts. Testing and Inspection
- If the MIL blinks at a steady rate, a severe misfire condition could possibly exist.
- If the MIL blinks erratically, an intermittent open B+ to the bulb or an intermittent short to ground in the MIL circuit exist. Also, the PCM can reset while cranking if battery voltage is low.