Case IH 4376 – Engine Control Unit (ECU) or Aftertreatment / Dosing Control Unit (DCU): DEF Pump Direction Valve / SCR Reversing Valve Failure

Electrical or temperature fault on the low side of the DEF (Diesel Exhaust Fluid) pump direction valve (SCR reversing valve).

• Steiger T4B
• Magnum
• Steiger
• Puma
• Maxxum
• Farmall (110A, 130A, 140A)
• Axial-Flow series (5140, 6150, 7150, 9230)
• Patriot series (2250, 3240, 3340)

1. 1

   Visually inspect the wiring harness leading to the DEF pump supply module for chafing, melting, or breaks.

2. 2

   Disconnect the DEF pump electrical connector and inspect for pushed pins, corrosion, or DEF fluid intrusion (which is highly corrosive and causes shorts).

3. 3

   Test the reversing valve circuit wires between the ECU/DCU and the DEF pump with a multimeter for continuity, shorts to ground, and shorts to battery voltage.

4. 4

   If FMI 12 or 31 is present (overheating cause): Check if the DEF pump is physically overheating or if the exhaust/ambient heat shielding around the pump is damaged.

1. 1

   Turn off machine and disconnect battery

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Locate DEF pump supply module

   Locate the DEF pump supply module (typically mounted directly to the top or side of the DEF tank).

3. 3

   Clean area around pump

   Thoroughly clean the area around the pump to prevent dirt from entering the DEF tank.

4. 4

   Disconnect electrical harness

   Disconnect the electrical harness from the pump.

5. 5

   Disconnect and cap DEF lines

   Disconnect the DEF suction, pressure, and return lines. Cap the lines immediately to prevent crystallization and contamination.

6. 6

   Remove DEF pump

   Unbolt the DEF pump from its mounting bracket or tank flange and remove it.

7. 7

   Install new DEF pump

   Install the new DEF pump / dosing module and torque the mounting bolts to OEM specifications.

8. 8

   Reconnect lines and harness

   Reconnect the DEF lines and the electrical harness.

9. 9

   Reconnect battery

   Reconnect the battery.

10. 10

    Clear fault code

    Connect a diagnostic scan tool to clear the 4376 fault code.

11. 11

    Program and test new module

    The new DEF pump module will likely need to be programmed/calibrated to the vehicle's ECU using the dealer diagnostic tool. Run a system prime and dosing test to ensure there are no leaks and that the reversing valve operates correctly upon shutdown.