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

The Engine Control Module (ECM) has detected that the electrical circuit responsible for activating the fuel lift pump relay is drawing more current than expected. This over-current condition is typically caused by a short circuit in the wiring, an internal failure of the relay itself, or a failing fuel lift pump motor drawing excessive amperage. This fault may prevent the fuel pump from operating correctly, directly affecting engine performance.

• Tier 3 engines
• Tier 4a engines
• Tier 4B engines
• T8 series
• T8.275
• T8.300
• T8.330
• T8.360
• T8.390
• T8.420
• TC45

1. 1

   Check Fuses: Inspect all related fuses for the fuel system and ECU. On many New Holland tractors, the main fuse panel is located in the cab, often under the shifter console or on a side pillar. There may also be a fuse box in the engine compartment. A blown fuse is a strong indicator of an over-current situation.

2. 2

   Inspect Wiring: Carefully examine the wiring harness connected to the fuel lift pump and the fuel lift pump relay. Look for any signs of physical damage, such as chafing, melting, or corrosion, which could cause a short circuit to the chassis ground. Pay close attention to areas where the harness may rub against the frame or engine components.

3. 3

   Inspect the Relay: Locate the fuel lift pump relay. Its location can vary, but it is typically in a fuse and relay box in the cab or engine compartment. Check for any visible signs of overheating, such as a melted casing or discolored terminals.

4. 4

   Test the Fuel Lift Pump: A faulty fuel lift pump drawing excessive current can trigger this code. Disconnect the pump and check its internal resistance with a multimeter. Compare the reading to the manufacturer's specifications if available. Alternatively, you can momentarily power the pump with a separate power source to check its operation, but be cautious of the current draw.

1. 1

   Confirm the Fault

   Use a diagnostic tool to confirm that fault code 3399 is active or stored in the ECU. Note any other fault codes that may be present, as they could be related.

2. 2

   Safety First

   Disconnect the battery before performing any electrical repairs to prevent accidental shorts.

3. 3

   Locate Components

   Identify the fuel lift pump, fuel lift pump relay, and the relevant fuses. On New Holland T8 series tractors, the fuse and relay panels are typically located behind the operator's seat or in the engine compartment.

4. 4

   Test the Relay Circuit

   Remove the fuel lift pump relay. With the key in the 'on' position, use a multimeter to check for battery voltage at the appropriate terminal in the relay socket (this is the power supply for the relay coil). Check for continuity to ground on the ground terminal for the relay coil. Inspect the switched power circuit for a short to ground. With the relay removed, check for continuity between the wire leading to the fuel lift pump and the chassis ground. There should be no continuity.

5. 5

   Isolate the Fault

   If a short to ground is detected in the power circuit to the pump, disconnect the fuel lift pump and re-check. If the short disappears, the fuel lift pump is faulty and needs to be replaced. If the short remains with the pump disconnected, the fault lies in the wiring harness between the relay and the pump. If the relay itself is suspected, you can swap it with a known good relay of the same type.

6. 6

   Replace Faulty Components

   Replace the identified faulty component (relay, fuel lift pump, or wiring harness) with a new, genuine OEM part if possible.

7. 7

   Clear Fault Codes and Verify Repair

   After completing the repairs, reconnect the battery. Use a diagnostic tool to clear the fault code from the ECU. Start the engine and let it run to ensure the fault does not reappear.