GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Chevy C Cab/Chassis HD (GMT 400) 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 Water-in-Fuel Lamp Inoperative

Circuit Description

The fuel manager/filter assembly consists of the fuel heater, the water-in-fuel sensor and a filter. The filter contains the coalescer (the device that combines small droplets of water into larger ones) and the filter/separator.

A fuel lift pump delivers diesel fuel from the tank to the fuel filter. As fuel enters the filter, the fuel passes first though the fuel heater. The heater contains a thermostatic switch, which opens or closes to turn the heater OFF or ON, depending on the temperature of the fuel.

The fuel then passes through the filter and the water coalescer, where the droplets of water in the fuel combine into larger drops, that fall into the water reservoir in the filter. When fuel flows from the fuel manager/filter assembly to the injection pump, the fuel is clean and free of water.

The solid state water-in-fuel sensor supplies voltage to a probe. When the probe touches water, the module closes a switch. This completes a circuit to ground and lights the water-in-fuel lamp.

A circuit in the water-in-fuel module grounds the lamp briefly to test the bulb each time the system is turned ON.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step determines if the ignition feed circuit is open.

    2.

  2. This step determines if the ground circuit is OK.

    3.

  3. This step determines if the fuse, bulb, and wiring are OK.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Turn ON the ignition, with the engine OFF.

Does the water In fuel light come ON briefly?

Go to Step 6

Go to Step 3

3

  1. Disconnect the water-in-fuel sensor.
  2. With the J 35616-200 Unpowered Test Light connected to ground, probe terminal A.
  3. Verify that the ignition is ON, with the engine OFF.

Does the test lamp illuminate?

Go to Step 4

Go to Step 7

4

With a J 35616-200 , jumper the harness terminals A and C with the ignition still ON.

Does the test lamp illuminate?

Go to Step 5

Go to Step 9

5

With a J 35616-200 connected to ground, probe terminal B of the harness connector.

Does the test lamp illuminate?

Go to Step 8

Go to Step 10

6

Operate the vehicle under which the system was noted.

Does the system operate properly?

System OK

Go to Step 2

7
  1. Check the ignition feed circuit for an open.
  2. If a problem is found, repair as necessary.

Did you find and correct the condition?

Go to Step 12

--

8
  1. Check for a poor feed connection at the sensor.
  2. If a problem is found, repair as necessary.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

9
  1. Check the ground circuit for an open.
  2. If a problem is found, repair as necessary.

Did you find and correct the condition?

Go to Step 12

--

10

Repair the open in the lamp circuit.

Did you complete the repair?

Go to Step 12

--

11

Replace the water-in-fuel sensor. Refer to Water in Fuel Indicator Sensor Replacement .

Did you complete the replacement?

Go to Step 12

--

12

Operate the vehicle under which the original problem was noted.

Does the system operate properly?

System OK

Go to Step 2

13
  1. Start the engine.
  2. Operate the vehicle within the Conditions that produced the failure.

Does the system operate normally?

Go to Step 14

Go to Step 2

14

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK