Circuit Description
There should always be a steady Malfunction Indicator Lamp (MIL) when the ignition switch is on and the engine is not running. The ignition voltage is supplied directly to the indicator bulb. The Engine Control Module (ECM) controls the lamp by grounding the control circuit via an internal solid state device called a driver.
Diagnostic Aids
| • | Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals. |
| • | An intermittent may be caused by the following: |
| - | Corrosion |
| - | A mis-routed harness |
| - | A rubbed through wire insulation |
| - | A broken wire inside the insulation |
Refer to Symptoms for the Intermittents.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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This step determines whether you were sent here because of an inoperative MIL, or because of a MIL that is always on with no DTCs set.
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This verifies that the B+ circuit is functional from the engine controls power relay.
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If the other indicator lamps in the instrument cluster are functioning, the feed circuit is OK.
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This step verifies that the MIL is on with no DTCs set. If a DTC is displayed, return to the Powertrain On-Board Diagnostic (OBD) System Check.
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If the MIL is on with the ECM connected and off with the ECM disconnected, and no DTCs are set, there is a problem in the ECM.
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After the engine starts, the MIL should illuminate briefly and then go out. If the MIL remains on, go back to the Powertrain OBD System Check.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
Turn on the ignition with the engine off. Does the MIL illuminate? | -- | |||||||||
Disconnect the IAC Motor. Probe the switched B+ circuit in the IAC harness connector with the test light J 34142-B connected to battery ground. Does the test light illuminate? | -- | |||||||||
Check the fuse for the instrument cluster ignition feed circuit. Is the fuse OK? | -- | |||||||||
5 |
Is the MIL on? | -- | ||||||||
6 | Check for the following conditions:
Is the action complete? | -- | -- | |||||||
Use the scan tool in order to verify that no DTCs are set. Are there any DTCs displayed? | -- | |||||||||
Does the MIL illuminate? | -- | |||||||||
9 | Repair the short to ground in the MIL control circuit. Is the action complete? | -- | -- | |||||||
10 | Repair the short to ground in the feed circuit to the instrument panel indicator lamps. Is the action complete? | -- | -- | |||||||
11 | Check for a poor connections or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||||||||
12 |
Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | -- | |||||||
13 | Start the engine and observe the MIL. Does the MIL turn ON briefly and then turn OFF? | -- | The System is OK | Refer to Test Description |
