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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1850 (Engine Controls And Fuel - 2.4L (Lat) - Troubleshooting & Diagnosis) >> Fuel Pump Electrical Circuit Diagnosis >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the fuel pump relay.
  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 engine control module (ECM).
    • 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 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 primary fuel tank module.
  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 primary fuel tank module.
  7. If all circuits test normal, test or replace the fuel pump relay.
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