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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 428 (ENGINE CONTROLS - BASIC DIAGNOSTIC PROCEDURES)FUEL SYSTEMFUEL PUMP ELECTRICAL CIRCUIT DIAGNOSISTEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Test Description

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers in the diagnostic procedure.

  1. 2

    Command both the ON and OFF states. Repeat the commands as necessary.

  2. 3

    This step determines if the condition is located on the coil side or the switch side of the circuit.

  3. 4

    This step verifies that the PCM is providing voltage to the fuel pump relay.

  4. 5

    This step tests for an open in the fuel pump relay ground circuit.

  5. 6

    This step determines if a voltage is constantly being applied to the fuel pump relay.

  6. 12

    This tests for a grounded voltage supply circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump voltage supply circuit.

  7. 15

    This step jumps the fuel pump relay in order to activate the fuel pump.

  8. 16

    This step tests for an open in the fuel pump feed circuit between the in-line connector and the fuel pump relay.

  9. 17

    This step tests for an open or high resistance in the fuel pump ground circuit.

  10. 20

    This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.