Malfunction Indicator Lamp: Description and Operation

"CHECK ENGINE" LIGHT (Malfunction Indicator Light):

PURPOSE
The malfunction indicator light (MIL), located in the instrument panel, will come on to warn the driver if a malfunction occurs in the following circuits:
- ECM
- Heated front Oxygen sensor
- Volume Air-flow sensor
- Intake air temperature sensor
- Throttle position sensor
- Engine coolant temperature sensor
- Crankshaft position sensor
- Camshaft Position (TDC) sensor
- Barometric pressure sensor
- Injector
- Ignition coil, Power transistor
- Knock sensor
- EGR
- Ignition timing adjustment signal

OPERATION
The ECM stores a code for the fault. Immediately after the ignition switch is turned on, the MIL will light for 2.5 seconds to indicate that the light operates normally. When an irregular signal returns to normal the MIL goes out. Also, when the ignition switch is turned off, the light goes out. If the engine is re-started the light will not come back on until the fault re-occurs, but a code will be stored in the ECM memory.