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.

NOTE: Before proceeding with this step, drain any water from fuel system.

Turn ON the ignition, with the engine OFF. Does water-in-fuel light illuminate briefly, then go out? If yes, go to step 4. If no, go to next step.
Does water-in-fuel light stay ON? If yes, go to step 5. If no, go to.WATER-IN-FUEL LIGHT INOPERATIVE (6.5L)
Operate vehicle under conditions which problem was noted. Does system operate normally? If yes, system is okay. If no, go to step 2.
Disconnect water-in-fuel sensor harness connector. Turn ON the ignition, with the engine OFF. Probe Water-In-Fuel Indicator Control circuit at harness connector with Test Light (J 34142-B) connected to battery voltage. Does test light illuminate? If yes, go to next step. If no, go to step 7.
Repair short to ground in Water-In-Fuel Indicator Control circuit. After repairs, go to step 8.
Replace water-in-fuel sensor. After repairs, go to next step.
Start engine. Operate vehicle within conditions under which problem was noted. Does system operate normally? If yes, system is okay. If no, go to step 2.

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.

Safety Warning

Diagnostic Procedure