Massey Ferguson E4332.E – ECU (Engine Control Unit): DEF System Pressure High

The system has detected that the pressure of the Diesel Exhaust Fluid (DEF) within the dosing system is exceeding the normal operating parameters. In the AGCO Power DNOX2.2 (Bosch Denoxtronic 2.2) system, dosing pressure is generated by pumping DEF against a throttle cavity located inside the Supply Module's backflow connector. High pressure typically indicates a restriction or blockage in the return circuit rather than a failed pump.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• MF 5608
• MF 5609
• MF 5610
• MF 5611
• MF 5612
• MF 5613
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• MF 7619
• MF 7620
• MF 7622
• MF 7624
• MF 7626
• MF 8650
• MF 8660
• MF 8670
• MF 8680
• MF 8690

1. 1

   Depressurize the System: Ensure the DEF pressure has decreased before any diagnostic or repair actions.

2. 2

   Check the Backflow/Return Circuit: Inspect the return line from the Supply Module to the DEF tank for kinks, pinched hoses, or crystallization blockages.

3. 3

   Inspect the Throttle Cavity: Check for clogs inside the Supply Module's backflow connector, as pressure is generated against this cavity.

4. 4

   Avoid Unnecessary Replacements: Do not change the dosing module (injector) immediately, as it is rarely the cause of pressurizing problems.

5. 5

   Check for Contamination: Ensure the system has not been contaminated by diesel fuel, oil, or substandard DEF, which causes crystallization.

1. 1

   Safety First

   Turn off the machine and wait for the DEF system to purge and depressurize completely. Do not use high-pressure water washing on any DNOX2.2 system components.

2. 2

   Clear the return line

   Disconnect the DEF return line from the Supply Module to the tank. Flush or clear the line of any crystallized urea.

3. 3

   Clean the throttle cavity

   Inspect and clean the throttle cavity located inside the Supply Module's backflow connector. Crystallization blockages can often be cleaned with warm distilled water instead of replacing the entire pump assembly.

4. 4

   Replace the DEF filter

   Remove the main filter cover on the Supply Module. Extract the old DEF filter and the equalizing element (frost compensation membrane). Clean the housing and install a new OEM filter kit with new O-rings to ensure a tight seal.

5. 5

   Reassemble and test

   Reconnect all DEF lines. Turn the key cycle on to allow the After-Treatment Control Module (ACM) to command the pump to prime. Monitor the DEF pressure via diagnostic software to verify it has returned to normal operating range.