Massey Ferguson 521008.01 – Engine Control Unit (ECU): DEF Pressure Issue (ECU)

This indicates that the system is failing to maintain or read the correct pressure of Diesel Exhaust Fluid (DEF/AdBlue) required for proper dosing into the Selective Catalytic Reduction (SCR) system. When this occurs, the tractor will likely enter a derate mode to comply with emissions regulations.

• 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

1. 1

   Perform a system reset by turning off the tractor and waiting 30 seconds. Restart the machine to see if the code clears automatically.

2. 2

   Ensure the DEF tank is full of clean, unexpired fluid. Contaminated or crystallized DEF is a leading cause of pressure drops.

3. 3

   Inspect the wiring harness and connectors going to the DEF pump and DEF pressure sensor for corrosion, moisture, or loose pins.

4. 4

   Check the DEF filter. A clogged filter will restrict flow and cause a low-pressure fault.

5. 5

   Inspect the DEF suction and backflow lines for physical leaks, blockages, or crystallization.

1. 1

   Disconnect power

   Disconnect the battery before servicing DEF electrical components to prevent shorting.

2. 2

   Clean or replace connectors

   If the DEF pump or sensor connector is corroded, cut back the harness and splice in a weather-sealed OEM replacement connector.

3. 3

   Replace the DEF filter

   If the filter hasn't been changed recently, remove the filter housing cap, extract the old cartridge, clean the housing, and install a new DEF filter cartridge.

4. 4

   Test or replace the sensor

   If the wiring and filter are good, the DEF pressure sensor may be sending out-of-range plausibility signals to the ECU. Replace the sensor.

5. 5

   Replace the DEF pump

   If the sensor is reading correctly but the system genuinely cannot build pressure, the DEF pump has failed internally and must be replaced.

6. 6

   Clear codes

   Reconnect the battery. If the code does not clear on startup, you may need to use an AGCO EDT (Electronic Diagnostic Tool) to clear the stored fault from the ECU.