Malfunction Indicator (Check Engine) Lamp

OPERATION
The PCM provides the ground path for the malfunction indicator lamp (Check Engine lamp in the gauge cluster on the instrument panel). The lamp comes on each time the ignition key is turned ON and stays on for a 3 seconds bulb test.

The MIL lamp 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 malfunction indicator lamp 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 inputs from other sensors for the incorrect signals.

If the PCM detects active engine misfire sever enough to cause catalyst damage, it flashes the malfunction indicator lamp (Check Engine light). At the same time the PCM also sets a diagnostic trouble code.

Signals that can trigger the Malfunction Indicator (Check Engine) Lamp:
- Camshaft Position Sensor
- Cam/Crank Relationship (Timing Belt)
- Deteriorated Catalytic Convertor
- Deteriorated Fuel Control System
- Deteriorated EGR System
- Deteriorated EVAP System
- Deteriorated Heated Oxygen Sensor
- Engine Coolant Temperature Sensor
- Engine Misfire
- Fuel Injectors
- Heating Element in Oxygen Sensors
- Idle Air Control Motor
- Idle Speed
- Ignition Coils
- Intake Air Temperature Sensor
- Manifold Absolute Pressure Sensor
- Park/Neutral Switch
- PCM Internal Self Test
- Power Steering Switch
- Radiator Fan Relay
- Throttle Position Sensor
- Torque Convertor Clutch Solenoid
- Vehicle Speed Sensor

The malfunction indicator lamp can also display diagnostic trouble codes. Cycle the ignition switch on, off, on, off, on, within five seconds and the PCM displays any diagnostic trouble codes stored in memory.