Circuit Description
Voltage is supplied to the malfunction indicator lamp (MIL) internally by the instrument panel cluster (IPC). 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 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 the 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 as 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. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Turn ON the ignition, with the engine OFF. Is the instrument cluster completely inoperative? | -- | Go to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages, and Console | Go to Step 3 |
3 |
Does the malfunction indicator lamp (MIL) turn ON and OFF when commanded with a scan tool? | -- | Go to Intermittent Conditions | Go to Step 4 |
4 | Inspect the fuse that supplies voltage to the cluster. Is the fuse open? | -- | Go to Step 11 | Go to Step 5 |
5 |
Is the voltage less than the specified value? | 1 V | Go to Step 6 | Go to Step 12 |
6 |
Is the MIL illuminated? | -- | Go to Step 10 | Go to Step 7 |
7 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 13 |
8 | Test the MIL control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 16 | Go to Step 9 |
9 | Test for an intermittent and for a poor connection at the IPC. 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 16 | Go to Step 14 |
10 | Test for an intermittent and for a poor connection at the ECM. 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 16 | Go to Step 15 |
11 | Test all circuits and components that use this voltage supply for excessive current draw. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | -- |
12 | 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 16 | -- |
13 | Repair the open in the voltage supply circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 16 | -- |
14 | Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | -- | Go to Step 16 | -- |
15 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 16 | -- |
16 |
Does the MIL operate correctly? | -- | Go to Step 17 | Go to Step 2 |
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | |
