Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the harness connector at the headlamp switch.
- Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and B+.
- If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
- Ignition ON, verify the scan tool Dimming Control Signal parameter is less than 0.1 volts.
- If greater than the specified range, test the signal circuit terminal 13 for a short to voltage. If the circuit tests normal, replace the BCM.
- Ignition ON, test for 12 volts between the I/P dimming voltage reference circuit terminal 15 and ground.
- If less than the specified value, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
- Install a 3A fused jumper wire between the signal circuit terminal 13 and the voltage reference circuit terminal 15. Verify the scan tool BCM Dimming Control Signal parameter is greater than 2.6 volts.
- If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
- If all circuits test normal, test or replace the headlamp switch.