Massey Ferguson 4374.14 – Engine Control Unit (ECU): DEF pump motor speed permanent deviation

The controller has detected that the Diesel Exhaust Fluid (DEF) pump motor is running at a speed higher than normal to maintain a given DEF pressure, or there is a permanent deviation from the expected pump speed. This typically points to a restriction in the DEF lines, fluid contamination, or an internal failure of the DEF pump itself.

• 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
• 4700 series
• 5600 series
• 5700 series
• 7600 series
• 7700 series

1. 1

   Check for accompanying codes like SPN 4334 (DEF pressure sensor) or SPN 4375 (DEF pump motor control) and diagnose those electrical/sensor faults first

2. 2

   If operating in ambient temperatures below 12°F (-11°C), verify that the DEF fluid is not frozen in the tank or lines

3. 3

   Inspect the DEF tank vent tube for any blockages or restrictions that could create a vacuum

4. 4

   Inspect DEF lines for physical restrictions, kinks, or air leaks in the supply line and pressure line

5. 5

   Use a DEF test strip to check for diesel fuel or oil contamination in the DEF fluid

1. 1

   Clear Restrictions

   If a blocked vent tube or kinked DEF line was found during diagnostics, clear the blockage or replace the damaged line. Clear the fault codes and test run the machine.

2. 2

   Address Contamination

   If the DEF test strip indicates oil or diesel contamination, the entire system is compromised. Drain the system and replace the DEF tank, DEF tank header, all DEF supply/return lines, and the DEF pump. Refill with fresh, high-quality DEF.

3. 3

   Replace the DEF Pump

   If the fluid is clean, the lines are clear, and the code persists, the DEF pump has likely suffered an internal failure. Disconnect the battery, relieve any residual pressure in the DEF lines, and disconnect the electrical harness and DEF fluid lines from the pump assembly. Unbolt the old pump and install the new unit. Reconnect lines and harnesses, ensuring absolute cleanliness. Reconnect the battery, prime the system, and use a diagnostic service tool to clear the codes and run an SCR system self-check.