Circuit/System Testing (w/LY6)
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 fuel pump relay.
- Ignition ON, verify that a test lamp illuminates between the ground circuit terminal and B+.
- If the test lamp does not illuminate, test the ground circuit for a short to voltage or an open/high resistance.
- Verify that a test lamp does not illuminate between the ground circuit terminal and the control circuit terminal.
- If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Remove the test lamp.
- Command the fuel pump relay ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is OK.
- If not the specified value, test the fuel pump relay control circuit for a short to ground. If the circuit tests normal, replace the ECM.
- Install a 3A fused jumper wire between the fuel pump relay control circuit terminal and the ground circuit terminal. Command the fuel pump ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is Fault.
- If not the specified value, test the fuel pump relay control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the fuel pump relay.