New Holland ENG 3966 – ENGINE ECU: Water in fuel filter failure

The Water-in-Fuel (WIF) sensor has detected that the water level in the fuel filter/water separator has reached a point where it needs to be drained. Alternatively, this code can trigger if there is a circuit failure, voltage irregularity, or physical failure of the WIF sensor itself.

• L150
• L160
• L170
• L175
• L190
• L216
• L218
• L220
• L221
• L223
• L225
• L228
• L230
• L234
• C227
• C232
• C238
• B90B
• B95B
• B100B
• B110B
• B115
• T4
• T5
• T6
• T7

1. 1

   Check the fuel filter/water separator bowl for visible water separation or heavy fuel contamination

2. 2

   Open the drain valve at the bottom of the fuel filter/water separator to drain any accumulated water

3. 3

   Inspect the wiring harness and connector leading to the Water-in-Fuel sensor for disconnected wires, corrosion, or shorts that could cause a false reading

4. 4

   Verify the sensor voltage. If the voltage is out of range (too high or too low) despite the filter being empty of water, the sensor itself has likely failed

1. 1

   Drain the Separator

   Locate the primary fuel filter/water separator. Place a catch pan underneath and open the petcock/drain valve to empty the water. Close the valve and prime the fuel system. If the code clears, no further repair is needed.

2. 2

   Replace the Filter

   If the fuel is heavily contaminated with water or debris, remove the spin-on fuel filter/water separator element and replace it with a new one.

3. 3

   Replace the Sensor

   If draining the filter does not clear the ENG 3966 code, and the wiring is intact, the WIF sensor has failed. Unscrew the sensor from the bottom of the filter housing (note: have a catch pan ready for fuel spillage) and install a new OEM Water-in-Fuel sensor.

4. 4

   Clear Codes

   Turn the key to the ON position to allow the Engine ECU to run a system check, or use a diagnostic tool to clear the inactive fault code.