Massey Ferguson E4374.14 – Engine ECU: DEF Pump Speed Issue (ECU)

DEF pump motor speed is higher than normal for a given DEF pressure. This typically indicates an under-pressurized DEF system, which causes the pump to over-speed in an attempt to build pressure. It is usually caused by a restriction in the DEF lines, air entering the system, frozen DEF, or an internal failure of the DEF pump itself.

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

1. 1

   Check for related codes (such as SPN 4334 for DEF pressure or SPN 4375 for DEF pump control signals) and diagnose those electrical/sensor faults first

2. 2

   In cold climates (below 12 degrees F / -11 degrees C), verify that the DEF fluid is not frozen, which will starve the pump and cause it to over-speed

3. 3

   Inspect the DEF tank vent tube for blockages or restrictions and clear any debris if found

4. 4

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

5. 5

   Visually inspect the DEF supply line (tank to pump) and pressure line (pump to dosing unit) for kinks, restrictions, cracks, or continuous air bubbles indicating a cracked suction line

1. 1

   Resolve Line/Vent Issues

   If the vent tube is clogged, clear it. If a DEF line is cracked or sucking air, replace the affected line.

2. 2

   Address Contamination

   If the DEF is contaminated with diesel or oil, you must replace the DEF tank, header, all supply/return lines, and the DEF pump, then refill with fresh DEF.

3. 3

   Replace the DEF Pump

   If the fluid is clean, the lines are intact, and the system is not frozen, the fault is due to an internal failure of the DEF pump (Supply Module). Disconnect the battery, drain the DEF fluid from the supply module area, disconnect the electrical harness and DEF fluid lines from the pump, unbolt and remove the old DEF pump, and install the new DEF pump and reconnect the lines and harness.

4. 4

   System Prime and Calibration

   Refill the system with clean DEF. Note: A new DEF pump/dosing module will require programming/calibration to the vehicle's ECU using a dealer diagnostic tool after replacement.