GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

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

Circuit/System Description

The hazard flashers may be activated in any power mode. The hazard switch is integrated into the driver information display panel. When the hazard switch is placed in the ON position, the radio communicates via serial data with the body control module (BCM) requesting the hazard lamps be activated. The BCM supplies battery voltage to all four turn signal lamps in an ON and OFF duty cycle. When the hazard switch is activated, the BCM sends a serial data message to the instrument panel cluster (IPC) requesting both turn signal indicators to be cycled ON and OFF.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool Hazards parameter while pressing and depressing the hazard switch. The parameter should change between Active and Inactive.

If the parameter changes as the switch is activated, replace the BCM.
If the parameter does not change as the switch is activated, replace the driver information display.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Driver Information Display Replacement
    •  Control Module References for BCM replacement, setup, and programming