Prowler V6-3.5L VIN G (1999)
Malfunction Indicator Lamp: Description and Operation
MALFUNCTION INDICATOR (CHECK ENGINE) LAMP - PCM OUTPUT
The PCM supplies the Malfunction Indicator (Check Engine) Lamp On/Off signal to the instrument panel through the CCD Bus. The CCD Bus is
a communications port. Various modules use the CCD Bus to exchange information.
The Service Engine Soon comes on each time the ignition key is turned ON and stays on for 3 seconds as a bulb test.
The Malfunction Indicator Lamp (MIL) stays on continuously when the PCM has entered a Limp-In mode or identified a failed emission
component. During Limp-in Mode, the PCM attempts to keep the system operational. The MIL signals the need for immediate service. In limp-in
mode, the PCM compensates for the failure of certain components that send incorrect signals. The PCM substitutes for the incorrect signals with
inputs from other sensors.
If the PCM detects active engine misfire severe enough to cause catalyst damage, it flashes the MIL. At the same time the PCM also sets a
Diagnostic Trouble Code (DTC).
For signals that can trigger the MIL (Check Engine Lamp) refer to On-Board Diagnostics.
The MIL can also display diagnostic trouble codes. Cycle the ignition switch on, off, on, off, on, within 5 seconds and any diagnostic trouble
codes stored in the PCM will be displayed. Refer to On-Board Diagnostics in Emission Control Systems Diagnostic Trouble Code Descriptions.
FUNCTIONAL DESCRIPTION
As a functional test, the Malfunction Indicator Lamp (MIL) illuminates at key-on before engine cranking. Whenever the Powertrain Control
Module (PCM) sets a Diagnostic Trouble Code (DTC) that affects vehicle emissions, it illuminates the MIL. If a problem is detected, the PCM
sends a message over the CCD Bus to the instrument cluster to illuminate the lamp. The PCM illuminates the MIL only for DTC's that affect
vehicle emissions. The MIL stays on continuously when the PCM has entered a Limp-In mode or identified a failed emission component or
system. The MIL remains on until the DTC is erased. Refer to the Diagnostic Trouble Code charts for emission related codes.
Also, the MIL either flashes or illuminates continuously when the PCM detects active engine misfire. Refer to Misfire Monitoring.
Additionally, the PCM may reset (turn off) the MIL when one of the following conditions occur:
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PCM does not detect the malfunction for 3 consecutive trips (except misfire and fuel system monitors).
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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.
