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 ignition switch.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 4 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the DLIS circuit fuse is open, test the signal circuit terminal 5 for a short to ground.
- Verify the scan tool Key In Ignition Status parameter is Key Out.
- If not the specified value, test the signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the BCM.
- Install a 3A fused jumper wire between the signal circuit terminal 5 and the B+ circuit terminal 4. Verify the scan tool Key in Ignition Status parameter is Key In.
- If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
- If all circuits test normal, test or replace the ignition switch.