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Home >> Cadillac >> 2010 >> STS 3.6 V, AWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls And Fuel - 4.6L (LH2) - Symptom Troubleshooting And Diagnosis) >> Fuel Pump Electrical Circuit Diagnosis >> Circuit/System Testing

Circuit/System Testing

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  1. With the ignition OFF, remove the fuel pump relay from the rear electrical center.
  2. Test for less than 5 ohms of resistance between the ground circuit and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the fuel pump relay control circuit 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 ECM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Inspect the fuel pump fuse.
    • If the fuel pump fuse is open, test for the following conditions:
      • A short to ground in the relay switch B+ circuit
      • A short to ground in the supply voltage circuit of the fuel pump
    • If the above circuits test normal, replace the fuel sender.
  5. Verify that a test light illuminates between the B+ circuit and ground.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  6. 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.
  7. If all circuits test normal, test or replace the fuel pump relay.
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