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Home >> Chevrolet >> 2006 >> Cobalt LTZ >> Repair and Diagnosis >> External Pages >> Different car >> Section 793 (Engine Controls And Fuel - 2.0L - DTC P0243 To DTC P0700) >> DTC P0627, P0628, or P0629 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the fuel pump relay.
  2. 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.
  3. 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.
  4. Remove the test lamp.
  5. 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.
  6. 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.
  7. Connect a 15A fused jumper wire between the positive voltage terminal at the battery and the fuel pump voltage supply circuit terminal and verify fuel pump activation.
    • If the fuel pump does not activate, test the fuel pump voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump.
  8. Ignition ON, connect a 15A fused jumper wire between the relay switch voltage supply circuit terminal and the fuel pump voltage supply circuit terminal and verify fuel pump activation.
    • If the fuel pump does not activate, test the relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and it's fuse is open, test or replace the relay.
  9. Ignition ON, verify that a test lamp illuminates between the relay coil ground circuit terminal and B+.
    • If the test lamp does not illuminate, test the relay coil ground circuit for an open/high resistance.
  10. If all circuits and the ECM test normal, test or replace the fuel pump relay.
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