CLAAS 7719h – ECU: Low Voltage Signal and Water in Fuel Detected

The Engine Control Unit (ECU) has detected a dual issue: the presence of water in the diesel fuel system and a low voltage signal in the water-in-fuel (WIF) sensor circuit. Water contamination can lead to poor engine performance, rough idling, engine hesitation, and severe damage to fuel injectors and the high-pressure fuel pump due to a lack of lubrication. The low voltage reading indicates an electrical fault such as a short to ground, damaged wiring, a failing sensor, or a sensor compromised by the water it detected.

• Lexion
• Jaguar
• Axion
• Arion
• Avero
• Scorpion

1. 1

   Verify water presence by draining the fuel/water separator into a clear container to see if water settles at the bottom

2. 2

   Inspect the fuel filter condition and check its last service date for clogging or age

3. 3

   Visually inspect the wiring harness and electrical connector at the water-in-fuel sensor for corrosion, damage, loose pins, or moisture intrusion

4. 4

   Check the machine's operator manual to identify and inspect any fuses related to the fuel system or engine sensors

1. 1

   Drain the Fuel/Water Separator

   If water was found, drain the separator until clean fuel is observed. On many systems, this may be enough to extinguish the warning light.

2. 2

   Address Fuel Contamination

   If a large amount of water was drained, the fuel tank itself may be contaminated and require draining and cleaning to prevent the issue from recurring.

3. 3

   Clean and Secure Electrical Connections

   If no water is present, or if the light remains on after draining, disconnect the water-in-fuel sensor connector. Clean the terminals of any corrosion and apply dielectric grease to protect the connection from moisture before securely reconnecting it.

4. 4

   Test the Sensor Circuit

   If the problem persists, use a digital multimeter to test the sensor's circuit. Check for the correct reference voltage (typically 5V) from the ECU to the sensor and test the sensor's output signal. Check for an open circuit or a short to ground in the wiring harness.

5. 5

   Replace the Water-in-Fuel Sensor

   If the wiring is intact and the sensor is receiving the correct voltage but not sending a proper signal back, the sensor itself is likely faulty and should be replaced.

6. 6

   Replace the Fuel Filter Assembly

   The water-in-fuel sensor is often integrated with or threaded into the fuel filter/water separator. It is best practice to replace the fuel filters when replacing the sensor.