Malfunction Indicator Lamp (MIL) Diagnosis

Malfunction Indicator Lamp (MIL) Diagnosis

Diagnostic Instructions

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

Circuit/System Description

The malfunction indicator lamp (MIL) illuminates to inform the driver that an emission system fault has occurred and the engine control system requires service. Ignition voltage is supplied directly to the MIL and, when the emission system fault occurs, the engine control module (ECM) turns the MIL ON by grounding the MIL control circuit. Under normal operating conditions, the MIL should be ON only when the ignition is ON and the engine is OFF.

Reference Information
Schematic Reference

* Engine Controls Schematics [1][2]Electrical Diagrams
* Instrument Cluster Schematics Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1 A4
Description and Operation

Hybrid Modes of Operation Description Hybrid Modes of Operation Description
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

Note: Any MIL requesting DTCs that may be set should be diagnosed first.

1. Ignition ON, engine running, command the MIL ON and OFF with a scan tool. The MIL should turn ON and OFF as commanded.
2. Command the MIL ON and OFF with a scan tool while observing the following control circuit status parameters:

* MIL Control Circuit Low Voltage Test Status
* MIL Control Circuit Open Test Status
* MIL Control Circuit High Voltage Test Status
Each parameter should display OK or Not Run.

Circuit/System Testing

1. Ignition ON, verify that the P16 Instrument Cluster warning indicators are illuminated.

• If the P16 Instrument Cluster indicators are not illuminated, test the ignition circuit terminal 31 for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, replace the P16 Instrument Cluster.

2. Ignition OFF, disconnect connector X1 at the K20 Engine Control Module.
3. Ignition ON, verify that the MIL is not illuminated.

• If the MIL is illuminated, inspect the MIL control circuit terminal 52 X1 for a short to ground. If the circuit tests normal, replace the P16 Instrument Cluster.

4. Ignition ON, verify that the MIL illuminates with a 3 A fused jumper between the K20 Engine Control Module MIL control circuit terminal 52 X1 and ground

• If the MIL does not illuminate, test the MIL control circuit terminal 52 X1 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

Repair Instructions

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

* Instrument Cluster Replacement Service and Repair
* Control Module References Control Module References for ECM replacement, setup, and programming