Lights On Indicator Malfunction

Lights On Indicator Malfunction

Diagnostic Instructions

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



Diagnostic Fault Information






Circuit/System Description

Ground is provided to the headlamp switch through the switch ground circuit and G304. With the headlamp switch in the ON position, the headlamps ON signal circuit from the body control module (BCM) is pulled low indicating the headlamps ON request. In response to this signal, the BCM will energize either the high or low beam relay illuminating the headlamps. At the same time when the high beam headlamps are ON, the BCM sends a message via GMLAN serial data to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator. Anytime the headlamps are ON and the ignition is OFF or the driver door is opened, the BCM will also request the IPC to turn on the LIGHTS ON INDICATOR located in the driver information center (DIC).


Diagnostic Aids

This diagnostic procedure assumes that the headlamps operate as described in Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation) .


Reference Information
Schematic Reference

Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning)for Scan Tool Information


Circuit/System Testing

Ignition ON, with a scan tool perform the display test for the IPC and observe the lights on indicator.

If the lights on indicator does not illuminate during the test or remains illuminated at all times, replace the IPC.
If the lights on indicator illuminates during the test, replace the BCM.



Repair Instructions

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


Programming and Relearning (Programming and Relearning)for BCM or IPC replacement, setup, and programming