Massey Ferguson E4332.31 – Engine ECU (AGCO SISU POWER EEM4): DEF System Pressure Did Not Drop During System Purge Cycle

When a modern diesel tractor is shut off, the DEF (AdBlue) pump module is designed to run in reverse for a short period (usually 60 to 120 seconds). This purge cycle empties the DEF fluid from the supply lines and the dosing injector back into the DEF tank to prevent the fluid from freezing, expanding, or crystallizing inside the lines. This fault code is triggered when the system's pressure sensor detects that the pressure did not drop as expected, meaning the lines were not successfully emptied.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• MF 4707
• MF 4708
• MF 4709
• MF 4710
• MF 5608
• MF 5609
• MF 5610
• MF 5611
• MF 5612
• MF 5613
• MF 5710 SL
• MF 5711 SL
• MF 5712 SL
• MF 5713 SL
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• MF 7619
• MF 7620
• MF 7622
• MF 7624
• MF 7626
• MF 7714
• MF 7715
• MF 7716
• MF 7718
• MF 7719
• MF 7720
• MF 7722
• MF 7724
• MF 7726
• 8600 Series
• 8700 Series

1. 1

   Operator Error Check (Battery Isolator): Ensure the operator is not turning off the battery disconnect/isolator switch immediately after turning off the ignition key. The Engine ECU requires battery power for up to 2 minutes after key-off to run the pump in reverse and complete the purge cycle.

2. 2

   Visual Line Inspection: Inspect the heated DEF supply and return lines for kinks, pinched areas, or rub points that could physically block the fluid from returning to the tank.

3. 3

   Listen for Pump Operation: Run the engine, shut it off normally (leaving the battery switch ON), and listen near the DEF tank. You should hear the DEF pump module running to purge the lines. If it is silent, the pump or its wiring/relays may have failed.

4. 4

   DEF Pressure Sensor Check: Using a diagnostic service tool, monitor the DEF pressure with the engine off. If the system is physically empty but the sensor still reads high pressure, the DEF pressure sensor is stuck or faulty.

5. 5

   Check for Crystallization: Disconnect the DEF lines at the pump and the injector to check for severe urea crystallization blocking the flow.

1. 1

   Verify Sensor Accuracy

   Connect your diagnostic tool. If the DEF pressure sensor is reading high pressure while the tractor is off and the lines are unpressurized, replace the DEF pressure sensor.

2. 2

   Clear Blockages

   If the sensor is accurate, disconnect the DEF lines. Flush any crystallized DEF from the lines and the dosing injector nozzle using warm distilled water. Replace any lines that are permanently kinked or damaged.

3. 3

   Inspect O-Rings

   Check the O-rings on the DEF quick connectors. Nicks or cuts can cause air ingress, which prevents the pump from creating the vacuum needed to pull the fluid back to the tank. Replace connectors or O-rings as needed.

4. 4

   Replace the Dosing Unit

   If the lines are clear, the sensor is accurate, and the pump fails to reverse/purge at shutdown, the AdBlue Injection Dosing Unit (DEF Pump) has failed internally and must be replaced.

5. 5

   System Reset

   After replacing parts, turn the ignition off for a minimum of 60 seconds, then back on. Clear the fault codes using the diagnostic tool.

6. 6

   Validation

   Start the engine, let the DEF system pressurize, and then shut the engine off. Wait and listen to ensure the purge cycle completes successfully without throwing the E4332.31 code.