Circuit Description
The battery positive voltage is supplied directly to the malfunction indicator lamp (MIL). The powertrain control module (PCM) 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.
MIL Function
| • | The MIL informs the driver that a malfunction has occurred. The vehicle should be serviced as soon as possible. |
| • | The MIL illuminates during a bulb test, and during a system test. |
| • | A diagnostic trouble code (DTC) will be stored if the diagnostic test requests a MIL. |
MIL Illumination
| • | The MIL will illuminate with ignition switch ON, and with the engine not running. |
| • | The MIL will turn OFF when the engine is started. |
| • | The MIL will remain ON if the self-diagnostic system detects a malfunction. |
| • | The MIL may turn OFF if the malfunction is not present. |
| • | If the MIL is illuminated and the engine stalls, the MIL will remain illuminated if the ignition switch is ON. |
| • | If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, and cycled ON again. |
Diagnostic Aids
If there is an intermittent condition, refer to Intermittent Conditions .
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 PCM.
-
This step determines if a voltage is being applied to the control circuit.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||
1 | Did you perform the 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 |
Is the MIL illuminated? | 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 | Connect a test lamp to a good ground in order to probe the MIL B+ circuit at the IPC harness connector. Does the test lamp illuminate? | Go to Step 8 | Go to Step 7 |
7 | Repair the open in the MIL B+ circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 14 | -- |
8 | Inspect for faulty connections at the harness connector of the IPC and repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 |
9 | Inspect for faulty connections at the harness connector of the IPC and repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections , and to 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 B+ 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 PCM. Refer to Powertrain Control Module Replacement . 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 |
