Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Procedure
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedure
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2002 Saturn Vue, 2002 Pontiac Montana, 2002 Pontiac Aztek, 2002 Oldsmobile Silhouette, and 2002 Oldsmobile Bravada. However, it is still accessible from the selected car via links, so may be relevant.
- Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 6.5L CAB & CHASSIS, CHEVY EXPRESS & SAVANA article. After performing Diagnostic System Check - Engine Controls, go to next step.
- Turn ON the ignition, with the engine OFF. Does water-in-fuel light come ON briefly? If yes, go to step 6. If no, go to next step.
- Disconnect water-in-fuel sensor. With Test Light (J 34142-B) connected to ground, probe terminal "A" (Pink wire). Verify ignition is ON, with the engine OFF. Does test light illuminate? If yes, go to next step. If no, go to step 7.
- With Test Light (J 34142-B), jumper harness terminals "A" (Pink wire) and "C" (Black wire) with ignition still ON. Does test light illuminate? If yes, go to next step. If no, go to step 9.
- With Test Light (J 34142-B) connected to ground, probe terminal "B" (Yellow/Black wire) of harness connector. Does test light illuminate? If yes, go to step 8. If no, go to step 10.
- Operate vehicle under which system was noted. Does system operate properly? If yes, system is okay. If no, go to step 2.
- Check Ignition Feed circuit for an open. If a problem is found, repair as necessary. After repairs, go to step 12.
- Check for a poor feed connection at sensor. If a problem is found, repair as necessary. Did you find and correct the condition? If yes, go to step 12. if no, go to step 11.
- Check Ground circuit for an open. If a problem is found, repair as necessary. After repairs, go to step 12.
- Repair open in Light circuit. After repairs, go to step 12.
- Replace water-in-fuel sensor. After repairs, go to step 12.
- Operate vehicle under condition which original problem was noted. Does system operate properly? If yes, system is okay. If no, go to step 2.
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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.