Malfunction Indicator Lamp Does Not Come ON at Ignition Switch ON (But Engine at Stop)

Malfunction Indicator Lamp Does Not Come ON at Ignition Switch ON (But Engine at Stop)

Wiring Diagram










Circuit Description

When the ignition switch is turned ON, ECM causes the main relay to turn ON (close the contact point). Then, ECM being supplied with the main power, turns ON the malfunction indicator lamp (MIL). When the engine starts to run and no malfunction is detected in the system, MIL goes OFF but if a malfunction was or is detected, MIL remains ON even when the engine is running.

Troubleshooting

1. MIL Power Supply Check

Turn ON ignition switch.

Do other indicator / warning lights in combination meter comes ON?
YES
Go to Step 2.
NO
"IG" fuse blown, main fuse blown, Ignition switch malfunction, "BLK/RED" circuit between "IG" fuse and combination meter or poor coupler connection at combination meter.

2. ECM Power and Ground Circuit Check

Does engine start?
YES
Go to Step 3.
NO
Go to Component Tests and General Diagnostics ECM Power and Ground Circuit Check.
If engine is not cranked, go to Cranking System Symptom Diagnosis.

3. MIL Circuit Check

Turn OFF ignition switch and disconnect connectors from ECM.
Check for proper connection to ECM at terminal "G04-4".
If OK, then using service wire, ground terminal "G04-4" in connector disconnected.

Does MIL turn on at ignition switch turned ON?
YES
Substitute a known-good ECM and recheck.
NO
Bulb burned out or "PPL/YEL" wire circuit open.