Massey Ferguson E4374.31 – Engine ECU: DEF Pump Speed Issue (ECU) / DEF pump motor not available for actuation.

This code indicates that the Engine Control Unit (ECU) is unable to actuate the DEF (AdBlue) pump motor, or there is a permanent deviation in the DEF pump motor speed. The system cannot build or maintain the necessary pressure to dose Diesel Exhaust Fluid into the SCR (Selective Catalytic Reduction) system, which will likely result in an engine derate to comply with emissions regulations.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624

1. 1

   Inspect the DEF doser, tailpipe, and pump area for white crust (crystallized DEF). This can cause blockages that prevent the pump from operating at the correct speed.

2. 2

   Check for air leaks or line damage. Inspect all quick connectors for wetness or rub-through. Long priming times or unstable dosing can trigger pump speed faults.

3. 3

   Listen for the DEF system purge operation at key-off. If the system is not purging correctly, fluid may be freezing or crystallizing inside the pump.

4. 4

   Check the wiring harness leading to the DEF pump. Ensure the pump is receiving proper voltage and the ground is secure.

5. 5

   Sample the DEF from the mid-tank using a clean sampler and test the concentration with a refractometer or test strips to ensure poor fluid quality isn't causing system strain.

1. 1

   Preparation

   Turn off the tractor, remove the key, and allow the exhaust system to cool completely. Ensure the DEF system has completed its automatic purge cycle (usually takes a few minutes after shutdown).

2. 2

   Locate the Pump

   Locate the DEF pump assembly, typically mounted near the DEF tank on the chassis.

3. 3

   Disconnect Electricals

   Carefully disconnect the main electrical harness connector from the DEF pump.

4. 4

   Disconnect Fluid Lines

   Disconnect the DEF supply, return, and doser lines. Note: Have a clean catch pan ready, as residual DEF will spill. Cap the lines immediately to prevent dirt ingress.

5. 5

   Remove the Pump

   Remove the mounting bolts securing the DEF pump to its bracket and remove the faulty unit.

6. 6

   Install the New Pump

   Mount the new DEF pump assembly and tighten the bolts to OEM torque specifications.

7. 7

   Reconnect Lines and Harness

   Reconnect the DEF fluid lines, ensuring the quick-connect fittings "click" securely into place. Reconnect the electrical harness.

8. 8

   System Prime and Clear Codes

   Turn the ignition key to the ON position (do not start the engine immediately) to allow the system to prime. Connect a diagnostic tool to clear the E4374.31 fault code.

9. 9

   Test Operation

   Start the engine and perform a forced manual dosing test or stationary regeneration via the diagnostic tool to verify the pump operates at the correct speed and there are no leaks.