General Description

MALFUNCTION INDICATOR LAMP (MIL)
The Check Engine or Malfunction Indicator Lamp (MIL) gives an indication when the Powertrain Control Module (PCM) has recorded a Diagnostic Trouble Code (DTC) for an On-Board Diagnostics II (OBDII) emissions-related circuit or component malfunction. The lamp is controlled by the instrument cluster circuitry based upon messages received from the PCM on the Chrysler Collision Detection (CCD) data bus.

There are some monitors that may take two consecutive trips, with a detected fault, before the MIL is illuminated. The MIL stays on continuously when the PCM has entered a Limp-In mode or identified a failed emission component.

Also, the MIL either flashes or illuminates continuously when the PCM detects active engine misfire.

Additionally, the PCM may reset (turn off) the MIL when one of the following occur:

^ PCM does not detect the malfunction for 3 consecutive trips (except misfire and Fuel system Monitors).

^ PCM does not detect a malfunction while performing three successive engine misfire or fuel system tests. The PCM performs these tests while the engine is operating within 375 RPM of and within 10% of the load of the operating condition at which the malfunction was first detected.

The MIL lamp can also be used to display a stored DTC by flashing on and off. Refer to Powertrain Management/Computers and Control Systems for more information on the PCM or the PCM inputs -- and on DTCs and their retrieval.

BULB CHECK
The PCM sends a lamp-on message for about three seconds when the ignition switch is turned to the On position as a bulb test.