Water-in-Fuel Lamp Diagnosis
Water-in-Fuel Lamp Diagnosis
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The Water In Fuel Sensor is an electrical contact switch that closes when the float arm of the sensor rises above the acceptable level of water in the fuel filter. The engine control module (ECM) monitors the voltage on the signal circuit of the water in fuel sensor. When the water in fuel sensor closes the circuit the ECM detects low voltage on the signal circuit and sends a serial data message to the instrument panel cluster to display the WATER IN FUEL SERVICE REQUIRED message.
Reference Information
Schematic Reference
Engine Controls Schematics (LGH or LML) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
Fuel System Description Fuel System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, command the water in fuel lamp ON and OFF with the scan tool. Verify the water in fuel lamp turns on and off with each command.
2. If the Water in Fuel Lamp is always ON proceed to the Circuit/System Testing section in this diagnostic
3. If the Water in Fuel Lamp is not ON or there is rust, corrosion, or water contamination in the fuel system proceed to the Component Testing section in this diagnostic.
Circuit/System Testing
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Ignition OFF, disconnect the harness connector at the B116 water in fuel sensor.
2. Test for less than 5 ohms between the ground circuit terminal 1 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool water in fuel switch parameter displays No Water.
• If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K20 engine control module.
Note: If fuse opens, repair the short to voltage in the signal circuit.
4. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the ground circuit terminal 1. Verify the scan tool Water in Fuel Sensor parameter displays Water.
• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 engine control module.
5. If all circuits test normal, test or replace the B116 water in fuel sensor.
Component Testing
1. Remove B116 water in fuel sensor from fuel filter assembly.
2. With a DMM, test for continuity between the B116 water in fuel sensor terminals while moving the float up and down manually with the water in fuel sensor drain pet cock pointed downward. The water in fuel sensor should have continuity when the float is in the raised position and should not have continuity when in the float is in the lowered position.
• If there is no continuity when the float is manually raised replace the B116 water in fuel sensor.
• If the switch does not open when the float is manually lowered replace the B116 water in fuel sensor.
3. Disconnect the DMM
4. Place the water in fuel sensor float in water. The water in fuel sensor float should float in water.
• If the water in fuel sensor float sinks in water replace the B116 water in fuel sensor.
5. Place the water in fuel sensor float in clean diesel fuel. The water in fuel sensor float should sink in the diesel fuel.
• If the water in fuel sensor float does not sink in diesel fuel, replace the B116 water in fuel sensor.
• If the B116 water in fuel sensor. functions normally, refer to the Circuit/System Testing section in this diagnostic.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Control Module References Control Module References for replacement, programming, and setup.