Massey Ferguson 4332.31 – Engine ECU: DEF System Pressure Did Not Drop During System Purge Cycle

When the tractor is shut down, the DEF pump module briefly reverses flow to purge fluid out of the lines and injector. If the system pressure does not drop during this cycle, the ECU logs this fault, indicating that the purge failed and fluid is likely trapped in the system.

• 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
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 7714S
• 7719S
• 8650
• 8660
• 8670
• 8680
• 8690
• 8727
• 8730
• 8732
• 8737

1. 1

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

2. 2

   Check the DEF injector/doser valve and the tank neck for urea crystallization, which can cause blockages.

3. 3

   Inspect the DEF filter and strainer inside the pump module for clogs that can restrict flow during the reverse purge cycle.

4. 4

   Test the DEF pressure sensor to ensure it is not falsely reading high pressure even when the system is empty.

5. 5

   Listen to the DEF pump module at shutdown to verify it runs briefly to pull fluid back. If it does not run, the pump's reversing function has failed.

1. 1

   Clear Blockages

   If any kinks or blockages are found in the DEF lines, reroute or replace the damaged lines. Clean any crystallized DEF from the injector nozzle using warm de-ionized water.

2. 2

   Replace the DEF Filter

   Open the DEF pump module housing and replace the main DEF filter cartridge (and clean the strainer) to ensure unrestricted flow.

3. 3

   Replace the DEF Pump / Dosing Module

   If the lines are clear and the filter is new, but the pump still fails to reverse and purge at shutdown, the internal reversing valve or pump motor has failed. The DEF pump/dosing module must be replaced.

4. 4

   System Calibration

   After replacing the dosing module, use a diagnostic tool to clear the fault codes and run a manual DEF system test/purge cycle to verify the pressure drops correctly.