Malfunction Indicator Light

The Malfunction Indicator Light (MIL) is located on instrument panel and is labeled CHECK ENGINE. The MIL will illuminate if the Powertrain Control Module (PCM) detects a failure of a OBD-II emission related component. When this occurs, a Diagnostic Trouble Code (DTC) will be set into PCM memory.

When a malfunction has been detected in 2 consecutive drive cycles, the PCM will turn on the MIL and store a DTC in memory. If the same malfunction is not detected for 3 consecutive drive cycles, the PCM will turn the MIL off. The DTC will remain in Keep Alive Memory (KAM) for 40 drive cycles, then DTC will be purged from PCM memory. One exception is if a misfire malfunction is detected that may damage catalytic converter, the MIL will illuminate or flash immediately and DTC will be set.

If MIL remains on during engine cranking, it could indicate the PCM is not receiving CMP signal or the MIL circuit is shorted to ground. If MIL blinks, there may be a severe misfire being detected by PCM. To turn MIL off after a repair, a PCM reset command from the scan tool must be sent, or 3 consecutive drive cycles must be completed without any detected malfunction.