Malfunction Indicator Lamp (MIL) Always On

Malfunction Indicator Lamp (MIL) Always On

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provide an overview of each diagnostic category.

Circuit/System Description

Ignition 1 voltage is supplied directly 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 driver information center (DIC)/clock.

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 diagnostic.

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 no longer 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.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the ECM.
2. Ignition ON, observe the MIL.

• If the MIL is illuminated, test the MIL control circuit for a short to ground. If the circuits/connections test OK, replace the driver information center (DIC)/clock.

• If the MIL is not illuminated, replace the ECM.

Repair Instructions

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

* Clock Replacement
* Control Module References for engine control module replacement, setup, and programming Programming and Relearning