Malfunction Indicator Lamp Inoperative

WIRING DIAGRAM





DIAGNOSTIC CHART

There should always be a steady malfunction indicator lamp (MIL) when the ignition is "on" and engine stopped. Battery voltage is supplied directly to the light bulb. The Engine Control Module (ECM) will control the light and turn it on by providing a ground path through green wire to the ECM.

Engine runs OK, check:
- Faulty light bulb.
- Circuit open.
- Gage fuse blown. This will result in no meter lights, turn signal lights or reminder buzzer etc.

Engine cranks but will not run.
- Continuous battery - fuse or main fuse open.
- ECM ignition fuse open.
- Battery circuit to ECM open.
- Ignition circuit to ECM open.
- Poor connection to ECM.

Solenoids and relays are turned "ON" and "OFF" by the ECM, using internal electronic switches called "drivers". Solenoid and relay coil resistance must measure more than 20 Ohms. Less resistance will cause early failure of the ECM "driver".

Failure of outer load such as shorted mode can damage the ECM driver.

Before replacing ECM, be sure to check the coil resistance of all solenoids and relays controlled by the ECM. See ECM wiring diagram for the solenoid(s) and relay(s) and the coil terminal identification.

NOTE: Before replacing ECM use a digital multimeter and check resistance of each ECM controlled relay and solenoid coil. See ECM wiring diagram for coil terminal identification for solenoid(s) and relay(s) to be checked. Replace any relay or solenoid if the coil resistance measures less than 20 Ohms.