Malfunction Indicator Lamp: Description and Operation

Malfunction Indicator (MIL) Light Location:

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:
- ECU
- Oxygen sensor
- Air-flow sensor
- Intake air temperature sensor
- Throttle position sensor
- Engine coolant temperature sensor
- Crank angle sensor
- TDC sensor
- Barometric pressure sensor
- Detonation "Knock" sensor
- Ignition timing adjustment signal
- Injector
- EGR (California only)
- Ignition coil/Power transistor

Note:
The malfunction indicator light comes on whenever the ignition timing adjustment terminal is shorted to ground. Therefore, the light comes on when the terminal is grounded to adjust the ignition timing. This does not indicate a malfunction.

The ECU will store 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 ECU memory.