Massey Ferguson E521007.31 – Engine ECU (EEM4): SCR system ERROR: DEF pressure stabilisation failure

The DEF supply module is unable to build, maintain, or stabilize the required fluid pressure for the Selective Catalytic Reduction (SCR) dosing system. When this code is active, the system registers an emissions-related fault, which will typically trigger a warning lamp and result in an engine power derate after a defined period.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 4707
• 4708
• 4709
• 4710
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 7614 through 7626
• 7714 through 7726S
• 8600 Series
• 8700 Series

1. 1

   Inspect the DEF/AdBlue for contamination (dirt, diesel, or water) which can cause pump failure and pressure drops

2. 2

   Check the DEF supply module main filter for clogs causing pressure starvation

3. 3

   Inspect the heated DEF lines (suction, pressure, and backflow) for kinks, rub points, or nicked O-rings at quick connectors that could allow air ingress

4. 4

   Remove and inspect the SCR DEF injector for severe crystallization buildup altering system backpressure

5. 5

   Inspect the wiring harness to the DEF pump and pressure sensor for twisted pair signal wire issues, shorts to ground, or open circuits

1. 1

   Resolve fluid contamination

   If the DEF fluid is contaminated, drain the DEF tank completely, flush the tank, and refill with fresh, high-quality DEF.

2. 2

   Replace the DEF filter

   Regardless of the root cause, replace the DEF supply module main filter to ensure unrestricted flow to the pump.

3. 3

   Clean the DEF injector

   Clean any crystallized urea from the DEF injector nozzle using warm water.

4. 4

   Replace the DEF pump

   If lines are sealed, filter is new, and fluid is clean but pressure still cannot stabilize, replace the DEF supply module (pump) as it has failed internally.

5. 5

   Bleed and test system

   Use a compatible diagnostic tool (AGCO EDT or JPRO) to run a DEF System Leak Test and a DEF Pressure System Test to force the pump to prime and verify pressure stabilizes.

6. 6

   Clear codes

   Clear the E521007.31 fault code from the EEM4 ECU and reset the SCR system to lift the engine derate.