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.
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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 143 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING)FUEL SYSTEM (DIESEL)WATER-IN-FUEL LIGHT ALWAYS ON (6.6L)DIAGNOSTIC PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD
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 - 6.6L SIERRA & SILVERADO article. After performing Diagnostic System Check - Engine Controls, go to next step.
- Start and idle engine. Observe message center in instrument cluster. Does message center indicate water-in-fuel? If yes, go to next step. If no, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - TRUCKS article.
- Perform Water-In-Fuel Draining Procedure. See WATER-IN-FUEL DRAINING PROCEDURE (6.6L) . After performing procedure, go to next step.
- Start and idle engine. Observe message center in instrument cluster. Does message center indicate water-in-fuel? If yes, go to next step. If no, go to step 10.
- Disconnect water-in-fuel sensor. Does scan tool display Water-In-Fuel parameter is OFF? If yes, go to step 8. If no, go to next step.
- Turn OFF the ignition. Disconnect ECM. Probe Water-In-Fuel Indicator Control circuit with a test light connected to battery voltage. Does test light illuminate? If yes, go to next step. If no, go to step 9.
- Repair short to ground in Water-In-Fuel Indicator Control circuit. After repairs, go to step 10.
- Replace water-in-fuel sensor. After repairs, go to step 10.
- Replace ECM. Perform ECM relearn procedures. See PROGRAMMING in SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO article. After repairs, go to next step.
- Operate system in order to verify repair. Did you correct the condition? If yes, system is okay. If no, go to step 3.
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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.