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.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Hazard Switch Signal

1

1

--

--

Instrument Panel Lamps Supply Voltage

B2625 02

2

2

--

Hazard Switch Ground

--

1

1

--

1. Hazard Lamps Malfunction

2. Interior Backlighting Malfunction

Circuit/System Description

The hazard flashers may be activated in any power mode. The hazard switch is permanently grounded through G300. When the hazard switch is placed in the ON position, ground is applied through the hazard switch signal circuit to the body control module (BCM). The BCM supplies battery voltage to all 4 turn signal lamps in an ON and OFF duty cycle. When the hazard switch is placed in the ON position, the instrument panel cluster (IPC) receives a signal from the BCM via GMLAN requesting both turn signal indicators to be cycled ON and OFF.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

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

Scan Tool Reference

    •  Scan Tool Output Controls
    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the hazard switch.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal B and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool hazard lamp switch parameter is INACTIVE.
  5. If not the specified value, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal C and ground. Verify the scan tool hazard lamp switch parameter is ACTIVE.
  7. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, test or replace the hazard switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Hazard Warning Switch Replacement
    •  Control Module References for BCM replacement, setup, and programming

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.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Hazard Switch Signal

1

1

--

--

Instrument Panel Lamps Supply Voltage

B2625 02

2

2

--

Hazard Switch Ground

--

1

1

--

1. Hazard Lamps Malfunction

2. Interior Backlighting Malfunction

Circuit/System Description

The hazard flashers may be activated in any power mode. The hazard switch is permanently grounded through G305. When the hazard switch is placed in the ON position, ground is applied through the hazard switch signal circuit to the body control module (BCM). The BCM supplies battery voltage to all 4 turn signal lamps in an ON and OFF duty cycle. When the hazard switch is placed in the ON position, the instrument panel cluster (IPC) receives a signal from the BCM via GMLAN requesting both turn signal indicators to be cycled ON and OFF.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

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

Scan Tool Reference

    •  Scan Tool Output Controls
    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the hazard switch.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal A and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool hazard lamp switch parameter is INACTIVE.
  5. If not the specified value, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal D and ground. Verify the scan tool hazard lamp switch parameter is ACTIVE.
  7. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. If all circuits test normal, test or replace the hazard switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Hazard Warning Switch Replacement
    •  Control Module References for BCM replacement, setup, and programming