Malfunction Indicator Lamp: Description and Operation

Note: Malfunction Indicator Lamp (MIL), previously called Check Engine Lamp (CEL).

Location

In instrument panel "CHECK Engine" lamp.

Purpose

Caution: The malfunction indicator lamp signals the need for immediate service.

Lamp ON while vehicle is being driven informs driver that he has entered "Limp-In" mode. SEE CONTROL MODULE/LIMP-IN OPERATION.

Displays Diagnostic Trouble Codes (DTC's), stored in memory. SEE TESTING AND INSPECTION/ PROCEDURES/ EXTRACTING TROUBLE CODES.

Operation

Illuminates for three seconds when ignition switch is turned ON, (for bulb test).

PCM illuminates lamp if the signal received from a monitored circuit is outside of the set limits for that circuit.

^ PCM Illuminates by supplying signal through the CCD Bus. The CCD Bus is a communications port, used by various modules to exchange information.

^ The following input signals can trigger the Malfunction Indicator (Check Engine) Lamp if the PCM detects an input which is outside of the preset limits for that circuit;

^ Coolant Temperature Sensor

^ Manifold Absolute Pressure Sensor

^ Throttle Position Sensor

^ Battery Voltage Input

^ Charging System

^ An Emissions Related System