Massey Ferguson 4374.31 – ECU / ACM: DEF Pump Speed Issue (ECU)

There is a permanent deviation in the DEF pump motor speed, or the DEF pump motor is not available for actuation. The pump cannot reach the commanded speed or fails to respond, resulting in an under-pressurized DEF system.

• 4710
• 7724S
• 5712SL
• Interim Tier 4 (2012-2015)
• 7722
• 7722S
• 7615
• 5613
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7616
• 7618
• 5608
• 4708
• 7619
• 7626
• 7726S
• 7624
• 4707
• 4709
• 5711SL
• 7614
• 7718S
• 5610
• 7620
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 5612
• 7622
• 7720
• Tier 4 (2015-2021)
• 5611
• 7715S
• 5609
• 7724

1. 1

   Check for multiple active codes (specifically SPN 4334 / DEF Pressure Sensor or SPN 4375 / DEF Pump Control) and diagnose those electrical faults first

2. 2

   Inspect wiring and harness connections at the DEF dosing unit, DEF pump, ECU/ACM, and chassis aftertreatment harness for wire chafing, damage, or bent/corroded pins

3. 3

   Check for fluid contamination using a DEF test strip to look for diesel fuel or oil in the DEF tank. If contaminated, flush and clean the entire tank

4. 4

   Test for line restrictions by disconnecting the DEF pressure and suction lines from the pump and doser unit, then flushing with regulated shop air (maximum 40 PSI)

1. 1

   Relieve Pressure & Clean

   Turn the ignition OFF and wait for the DEF system to complete its purge cycle. Clean the area around the DEF pump module to prevent dirt ingress.

2. 2

   Replace the DEF Pump Filter & Screen

   Before replacing the entire pump, remove the DEF filter cover. Remove and replace the DEF pump module filter and the DEF pump inlet screen using an OEM service kit.

3. 3

   Replace the Pressure Relief Valve (PRV)

   If your specific pump module utilizes a serviceable PRV, replace it, as a failed PRV can cause the pump to overspeed to compensate for lost pressure.

4. 4

   Replace the DEF Pump / Dosing Module

   If the filter service does not resolve the 004374.31 code (indicating the motor itself is burnt out or mechanically failed), disconnect the electrical harness and fluid lines from the DEF pump. Unbolt the pump from its mounting bracket and install the new DEF pump module.

5. 5

   Prime and Clear Codes

   Reconnect all lines and harnesses. Turn the key ON to prime the system. Use your diagnostic tool to clear the fault codes and run an SCR ADS Self-Check or manual dosing test to verify the repair.