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 four turn signal lamps in an ON and OFF duty cycle. When the hazard switch is activated, the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) requesting both turn signal indicators to be cycled ON and OFF.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

1. Ignition ON, individually operate both the left and right turn signals. All applicable lamps should flash when in each turn signal position.

⇒	If any of the lamps do not flash, refer to Turn Signal Lamps and/or Indicators Malfunction.

2. Observe the scan tool Hazard Lamp Switch parameter while cycling the hazard switch. The parameter should change between Active and Inactive.

⇒	If the parameter does not cycle between the specified values, refer to Circuit/System Testing.

3. Press the hazard switch. All applicable lamps should flash.

⇒	If one or more lamps do not flash, replace the BCM.

1. Ignition OFF, disconnect the harness connector at the hazard switch.
2. Test for less than 5.0 ohms of resistance between the ground circuit terminal B and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Hazard Lamp Switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal C and the ground circuit terminal B. Verify the scan tool Hazard Lamp Switch parameter is Active.

⇒	If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the hazard switch.

Hazard Switch

1. Ignition OFF, disconnect the harness connector at the hazard switch.
2. Test for infinite resistance between the signal circuit terminal C and the ground circuit terminal B with the switch in the open position.

⇒	If not the specified value, replace the hazard switch.

3. Test for less than 2.0 ohms of resistance between the signal circuit terminal C and the ground circuit terminal B with the switch in the closed position.

⇒	If greater than the specified range, replace the hazard switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.