Malfunction Indicator Lamp (MIL) Diagnosis

Malfunction Indicator Lamp (MIL) Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Strategy Based Diagnosis
* Diagnostic Procedure Instructions

Circuit/System Description

Ignition voltage is supplied to the malfunction indicator lamp (MIL). The powertrain control module (PCM) turns the MIL ON by grounding the MIL control circuit.

Circuit/System Verification

The MIL should turn ON and OFF when commanded with a scan tool.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the instrument cluster.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit and ground.

^ If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, replace the instrument cluster.

3. Connect a test lamp between the control circuit and the ignition circuit.
4. Command the MIL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

^ If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the PCM.
^ If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the PCM.

5. If all circuits test normal, replace the instrument cluster.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Control Module References for PCM replacement, setup and programming Programming and Relearning
* Instrument Cluster Replacement