Circuit Description
Ignition voltage is supplied 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 cluster (IPC).
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 ECM. |
MIL Illumination
| • | The MIL will illuminate with ignition switch 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 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, then ON. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics or Engine Controls Schematics Connector End View Reference: Instrument Panel, Gages, and Console Connector End Views or Engine Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Command the malfunction indicator lamp (MIL) ON and OFF with a scan tool. Does the MIL turn ON and OFF when commanded with a scan tool? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 | Inspect the fuse that supplies ignition voltage to the cluster. Is the fuse open? | -- | Go to Step 10 | Go to Step 4 |
Is the MIL illuminated? | -- | Go to Step 9 | Go to Step 5 | |
5 |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 11 |
6 | Test the MIL control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 7 |
7 | Test the MIL control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 8 |
8 | Test for an intermittent and for a poor connection at the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 |
9 | Test for an intermittent and for a poor connection at the ECM. Refer to Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 |
10 | Repair the short to ground in the ignition voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 14 | -- |
11 | Repair the open in the ignition voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 14 | -- |
12 | Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 14 | -- |
14 | Command the MIL ON and OFF with the scan tool. Does the MIL turn ON and OFF when commanded with a scan tool? | -- | Go to Step 15 | Go to Step 2 |
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
