Volt

Malfunction Indicator Lamp (MIL) Diagnosis

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 vehicle is ON and the engine is OFF.

If the condition is intermittent, move the related harnesses and connectors with the vehicle ON and the engine OFF, and with the engine running while monitoring the scan tool MIL control circuit status parameters. The MIL control circuit status parameters will change from OK or Not Run to Malfunction if there is a condition with the circuit or a connection.

Schematic Reference

Connector End View Reference

Component Connector End Views

Description and Operation

Hybrid Modes of Operation Description

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

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

1. 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 control circuit status parameters listed below:

•	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.

3. Vehicle in Service Mode, command the MIL ON and OFF with a scan tool while observing the control circuit status parameters listed below:

•	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.

1. Vehicle in Service Mode, 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. Vehicle OFF, disconnect the harness connector X1 at the K20 engine control module.
3. Vehicle in Service Mode, observe the MIL. The MIL should not illuminate.

⇒	If the MIL is illuminated, test the control circuit terminal 52 X1 for a short to ground. If the circuit tests normal, replace the P16 instrument cluster.

4. Connect a 3 A fused jumper wire between the control circuit terminal 52 X1 and ground. The MIL should illuminate.

⇒	If the MIL does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 engine control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.