Massey Ferguson E521008.00 – Engine Control Unit (ECU): AdBlue™ or DEF system Pressure relief fault

The Selective Catalytic Reduction (SCR) system is unable to properly build, maintain, or relieve the pressure of the Diesel Exhaust Fluid (DEF). A failure to relieve pressure during the shutdown purge cycle can lead to fluid crystallization and blockages.

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

1. 1

   Verify the DEF tank level and check for contamination (e.g., dirt, diesel, or water)

2. 2

   Inspect the heated DEF supply and return lines for kinks, rub points, leaks, or damaged O-rings

3. 3

   Check the DEF filter inside the pump module for clogs

4. 4

   Listen to the DEF pump immediately after shutting off the tractor to ensure it runs in reverse briefly to purge fluid back to the tank

5. 5

   Remove the DEF dosing injector from the exhaust and check for severe urea crystallization blocking the nozzle

6. 6

   Inspect the wiring harnesses and connectors going to the DEF pump and DEF pressure sensor for corrosion, shorts, or open circuits

1. 1

   Clean the System

   If DEF contamination is found, drain the DEF tank completely, flush the system with distilled water, and refill with fresh, high-quality DEF.

2. 2

   Replace the Filter

   Regardless of the root cause, replace the main DEF filter element and its cover O-ring to ensure unrestricted flow.

3. 3

   Clear Blockages

   If crystallization is found in the lines or the injector nozzle, clean them using warm distilled water (do not use harsh chemicals or wire brushes on the injector tip).

4. 4

   Replace Faulty Components

   If the pump fails to build pressure or fails the purge cycle, replace the DEF Supply Pump Module. If the pressure sensor is reading out of range despite good mechanical pressure, replace the DEF Sensor.

5. 5

   Reprogramming/Calibration

   Note that replacing the DEF pump/dosing module often requires pairing or programming the new module to the ECU using a dealer diagnostic tool.

6. 6

   Clear Codes and Test

   Clear the E521008.00 code via the diagnostic tool and run a forced DEF system pressure/dosing test to verify the repair.