New Holland ENG 3421 – ENGINE ECU: Fuel Filter Sensor: Voltage Above Max Value

The Engine Control Unit (ECU) is receiving a voltage signal from the fuel filter sensor (which monitors for water-in-fuel or filter restriction) that exceeds the maximum allowable threshold. This typically points to an open circuit, a short to power, or an internally failed sensor.

• L213
• L216
• L218
• L220
• L221
• L223
• L225
• L230
• L318
• L320
• C227
• C232
• C238
• B90B
• B100B
• B95C
• B110B
• B115B
• W50C
• W60C
• T4 series
• T4.75
• T4.90
• T4.100
• T4.110
• T5 series
• T6 series
• T7 series

1. 1

   Visually inspect the fuel filter sensor to ensure it is not simply unplugged.

2. 2

   Inspect the wiring harness leading from the sensor to the Engine ECU for chafed wires, cuts, or areas shorting to a 12V power source.

3. 3

   Disconnect the sensor and check the connector pins for corrosion, water intrusion, or pushed-back pins causing an open circuit.

4. 4

   With the key ON and the sensor unplugged, use a multimeter to verify the reference voltage and ground at the harness connector. If wiring is intact but the code remains active when plugged in, the sensor has likely failed internally.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Drain Fuel

   Place a catch pan under the fuel filter assembly. Open the drain valve on the water separator to drain the fuel from the filter housing so it does not spill when the sensor is removed.

3. 3

   Remove the Sensor

   Disconnect the electrical pigtail from the fuel filter sensor. Carefully unscrew the sensor from the filter housing (many of these are M14 x 2mm threaded plastic or brass sensors).

4. 4

   Install the New Sensor

   Thread the new sensor into the housing. Be careful not to overtighten, especially if threading into a plastic bowl, to avoid cracking the housing.

5. 5

   Reconnect

   Plug the electrical connector back into the sensor harness. Reconnect the battery.

6. 6

   Prime the System

   Turn the key to the ON position (without starting the engine) for a few cycles to allow the electric lift pump to prime the fuel system and purge any air.

7. 7

   Clear Codes

   Start the machine and verify there are no fuel leaks. Use a diagnostic scan tool (or DTC eraser) to clear the ENG 3421 code from the Engine ECU, or allow the ECU to clear the active status after a successful key cycle.