Diagnostic Aids

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The water in fuel sensor illuminates the Water in Fuel message when there is water in the fuel system. Perform the Water in Fuel Draining procedure before performing the following test steps to accurately determine if a malfunction exists. Refer to Water-in-Fuel Draining Procedure in Engine Controls - 6.6L.
For intermittent diagnosis, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Water-in-Fuel Lamp Always On

Step	Action	Yes	No
Schematic Reference: Instrument Cluster Schematics , and Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views
1	Did you perform the Instrument Cluster Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Instrument Cluster
2	Does the Water In Fuel message remain illuminated in the driver information center after the displays test?	Go to Step 3	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
3	Turn the ignition OFF. Disconnect the water in fuel switch. Turn the ignition ON, with the engine OFF. Does the Water In Fuel message illuminate in the driver information center?	Go to Step 4	Go to Step 6
4	Test the signal circuit of the water in fuel switch for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 12	Go to Step 5
5	Install a scan tool. Turn the ignition OFF. Disconnect the water in fuel switch. Turn the ignition ON, with the engine OFF. With the scan tool, observe the Water In Fuel parameter in the PCM Engine Data 1 data list. Does the Water In Fuel parameter display Off?	Go to Step 8	Go to Step 7
6	Inspect for poor connections at the harness connector of the water in fuel switch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 12	Go to Step 9
7	Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 12	Go to Step 10
8	Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 12	Go to Step 11
9	Replace the water in fuel switch. Refer to the following: Water-in-Fuel Sensor Replacement in Engine Controls - 6.6L (LB7) Water-in-Fuel Sensor Replacement in Engine Controls - 6.6L (LLY) Did you complete the replacement?	Go to Step 12	-
10	IMPORTANT: Program the replacement PCM. Replace the PCM. Refer to the following: Engine Control Module (ECM) Replacement in Engine Controls - 6.6L (LB7) Engine Control Module (ECM) Replacement in Engine Controls - 6.6L (LLY) Did you complete the replacement?	Go to Step 12	-
11	IMPORTANT: Program the replacement IPC. Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement .Did you complete the replacement?	Go to Step 12	-
12	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 2