Malfunction Indicator Lamp: Description and Operation

The Check Engine or Malfunction Indicator Lamp (MIL) lights each time the ignition switch is turned to the ON position, and stays ON for three seconds as a bulb test. If the Powertrain Control Module (PCM) receives an incorrect signal or no signal from certain fuel or emission system related circuits or components, the lamp is turned ON. This indicates that the PCM has recorded a Diagnostic Trouble Code (DTC) in electronic memory for a circuit or component malfunction.