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 appropriate component.
- Ignition OFF, verify that a test lamp illuminates between the listed ground circuit terminal and B+.
- Rear window switch terminal F
- Headlamp switch terminal 8
- Transfer case shift control switch terminal 6
- Sunroof switch terminal 5
- Folding seat switch terminal 4
- Power liftgate open/close switch terminal C
- CJ3 HVAC control module terminal 2
- If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
- Connect a test lamp between the listed backlighting control circuit terminal and ground.
- Rear window switch terminal B
- Headlamp switch terminal 7
- Transfer case shift control switch terminal 5
- Sunroof switch terminal 3
- Folding seat switch terminal 5
- Power liftgate open/close switch terminal B
- CJ3 HVAC control module terminal 1
- Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states.
- If the test lamp is always OFF, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM.
- If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
- If all circuits test normal, test or replace the appropriate component.