Case IH 3137 (DTC 5255) - ECU – Engine Control Unit (ECU / EDC / ECM): Fuel metering unit has an open load error.

The ECM has detected an open circuit (a break in electrical continuity) on the circuit that controls the Fuel Metering Unit. Because the circuit is open, the ECM cannot command the valve to regulate the volume of diesel fuel entering the pumping plungers, which can result in a hard start, no start, or severe engine power loss.

• MAXXUM T4E
• 240 Series Axial-Flow Combines
• Puma Series
• Magnum Series (e.g., 235–340)
• Maxxum Series
• Steiger Series

1. 1

   Check if an external power supply (e.g., jump-starting) was connected; if so, disconnect it and test the system for normal operation

2. 2

   Visually inspect the wiring harness running from the Engine ECU to the Fuel Metering Unit for chafed wires, broken lines, or rodent damage

3. 3

   Disconnect the electrical plug at the Fuel Metering Unit and check for pushed-out pins, severe corrosion, or a loose connection

4. 4

   Using a multimeter, measure the resistance across the pins of the Fuel Metering Unit; if the reading shows infinite resistance (OL), the internal electromagnetic coil has failed open

1. 1

   Safety First

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

2. 2

   Clean the Area

   Thoroughly clean the area around the high-pressure fuel pump (usually a Bosch CP3 or CP4 pump) to prevent dirt from entering the fuel system.

3. 3

   Remove the Actuator

   Disconnect the electrical harness from the Fuel Metering Unit. Remove the mounting screws (typically Torx or Allen head) securing the unit to the high-pressure pump.

4. 4

   Extract the Unit

   Carefully pull the metering unit straight out of the pump housing.

5. 5

   Install the New Unit

   Lubricate the O-rings on the new Fuel Metering Unit with clean diesel fuel. Carefully insert it into the pump housing, ensuring the O-rings are not pinched.

6. 6

   Secure and Reconnect

   Install the mounting screws and torque them to the OEM specification. Reconnect the electrical harness plug.

7. 7

   Finalize

   Reconnect the battery. Turn the key to the ON position to allow the lift pump to prime the fuel system. Start the engine, check for leaks, and use a diagnostic service tool to clear the inactive 3137 / 5255 fault code.