New Holland ENG 3399 – Engine ECU: Engine Fuel Lift Pump relay driver over current fault

The engine control module has detected an excessive current draw (a short circuit or overload) on the circuit responsible for driving the fuel lift pump relay. When the current exceeds the driver's configured limit, the ECU typically shuts down the circuit to protect the power stage components.

• New Holland T8.275
• New Holland T8.300
• New Holland T8.360
• New Holland T8.380
• New Holland T8.390
• New Holland T8.410
• New Holland T8.420
• New Holland T8.435

1. 1

   Relay Inspection: Locate the fuel lift pump relay in the fuse/relay box. Check for moisture, corrosion, or debris around the relay terminals, which is a known cause for shorting.

2. 2

   Relay Coil Test: Remove the relay and measure the internal coil resistance with a multimeter to see if the relay itself has internally shorted.

3. 3

   Wiring Harness Check: Inspect the wiring harness between the Engine ECU and the fuel lift pump relay block. Look for chafed wires or damaged insulation causing a short to ground.

4. 4

   Fuel Lift Pump Current Draw: If the relay is functioning, the fuel lift pump itself may be failing and drawing excessive current, which can overheat the circuit and damage the relay. Test the pump's current draw against OEM specifications.

1. 1

   Disconnect Power

   Disconnect the battery to prevent electrical shocks or further damage to the ECU.

2. 2

   Swap the Relay

   Locate the fuel lift pump relay. Swap it with a known good relay of the exact same type/amperage from a non-critical circuit (like a work light relay) to see if the fault clears.

3. 3

   Test the Circuit

   If the fault persists with a good relay, use a multimeter to check the continuity of the wiring from the ECU pinout to the relay block. Repair any shorts to ground in the harness.

4. 4

   Replace the Pump (if necessary)

   If the wiring is intact but the pump is drawing too much current (or is seized/shorted), drain the fuel lines, disconnect the electrical connector to the pump, and replace the fuel lift pump assembly.

5. 5

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use an Electronic Service Tool (EST) to clear the fault codes, or cycle the key to see if the code moves from "Active" to "Stored".