Circuit Description
The battery positive voltage is supplied directly to the malfunction indicator lamp (MIL). The engine control module (ECM) turns the MIL ON by grounding the MIL control circuit. There should be a steady MIL with the ignition ON and the engine OFF.
MIL Operation
The MIL is located on the instrument panel (I/P).
MIL Function
| • | The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible |
| • | The MIL illuminates during a bulb test and a system test |
| • | A DTC will be stored if a MIL is requested by the diagnostic |
MIL Illumination
| • | The MIL will illuminate with ignition ON, and the engine not running |
| • | The MIL will turn OFF when the engine is started |
| • | The MIL will remain ON if the self-diagnostic system has detected a malfunction |
| • | The MIL may turn OFF if the malfunction is not present |
| • | If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition is ON. |
| • | If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition is cycled OFF, then ON. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the condition is with the MIL control circuit or the ECM.
-
This step determines if a voltage is constantly being applied to the control circuit.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||
1 | Did you perform the Engine Controls Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 | Inspect the fuse that supplies voltage to the MIL. Is the fuse open? | Go to Step 10 | Go to Step 3 |
Does the MIL illuminate? | Go to Step 9 | Go to Step 4 | |
Did the fuse in the jumper wire open? | Go to Step 11 | Go to Step 5 | |
5 |
Did you find and correct the condition? | Go to Step 14 | Go to Step 6 |
6 | Probe the MIL battery positive voltage circuit at the IPC harness connector with a test lamp connected to a good ground. Does the test lamp illuminate? | Go to Step 8 | Go to Step 7 |
7 | Repair the open in the MIL battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 14 | -- |
8 | Inspect for poor connections at the harness connector of the IPC and repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 |
9 | Inspect for poor connections at the harness connector of the ECM and repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 |
10 |
Did you complete the repair? | Go to Step 14 | -- |
11 | Repair the short to voltage in the MIL control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 14 | -- |
12 | Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | Go to Step 14 | -- |
13 | Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data . Did you complete the replacement? | Go to Step 14 | -- |
14 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
