Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

With the ignition OFF, remove the fuel pump relay from the electrical center.
Test for less than 5 ohms between the ground circuit and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit. Command the fuel pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the PCM.
- If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.
Inspect the fuel pump fuse.
- If the fuel pump fuse is open, test for the following conditions:
  - A short to ground in the supply voltage circuit of the fuel pump
  - A short to ground in the relay switch B+ circuit
    - If the above circuits test normal, replace the fuel sender.
Verify that a test lamp illuminates between the B+ circuit and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
- If the test lamp does not illuminate, repair the open in the battery positive voltage circuit.
Connect a 15A fused jumper wire between the B+ circuit and the supply voltage circuit of the fuel pump. Verify the fuel pump is activated.
- If the fuel pump does not activate, test for the following conditions:
  - An open/high resistance in the supply voltage circuit of the fuel pump
  - An open/high resistance in the ground circuit of the fuel pump
    - If the above circuits test normal, replace the fuel sender assembly.
If all circuits test normal, test or replace the fuel pump relay.