Malfunction Indicator Light (Mil)

MIL will illuminate if a failure occurs with Powertrain Control Module (PCM) or Transmission Control Module (TCM). If a failure occurs associated with TCM, see the AUTO TRANS DIAGNOSIS article in the AUTOMATIC TRANSMISSION section.

When ignition is turned on, MIL should come on. When engine is started, MIL should turn off after a couple of seconds. If MIL does not turn off after engine is started, or if MIL comes on while driving, retrieve Diagnostic Trouble Codes (DTCs). See RETRIEVING CODES  .

If MIL lights continuously, a malfunction is present that will cause an increase in emissions. If MIL starts to blink, a malfunction is present which may lead to catalytic converter damage. Repair these failures as quickly as possible. For some failures, MIL is only turned on after failure occurs after 2 successive trips with cold engine starts preceding failure.

Some failures will set a DTC which will never cause MIL to light. An example of a failure that could occur and not cause MIL to light would be a FUEL LEVEL TOO LOW signal generated.