Neon L4-2.0L VIN C (1998)
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 Check Engine lamp 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).
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.
