Massey Ferguson E4332.18 – ECU: DEF System Pressure Issue (ECU)

SCR (Selective Catalytic Reduction) metering module pressure is below the normal operating threshold. The system is failing to build or maintain the required pressure to properly inject Diesel Exhaust Fluid (DEF) into the exhaust stream.

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

1. 1

   Visually inspect the heated DEF supply and return lines for kinks, rub points, or nicks in the O-rings that could cause air ingress.

2. 2

   Check DEF fluid quality to ensure there is no diesel or water contamination, and verify the tank breather/cap is functioning to prevent vacuum locks.

3. 3

   Inspect the DEF filter/strainer for clogs that could restrict flow to the pump module.

4. 4

   Use a diagnostic tool to run an automated DEF System Pressure Test and monitor the DEF pressure sensor voltage to rule out an electrical fault.

1. 1

   Relieve Pressure

   Shut down the engine and allow the system to complete its automatic purge cycle (the pump reverses briefly at shutdown to empty the lines). Safely relieve any remaining DEF system pressure.

2. 2

   Clean the System

   Clean out any crystallized DEF fluid in the tank, lines, or around the metering module port. Ensure the port is completely free from debris.

3. 3

   Replace the DEF Filter

   Locate the DEF supply module filter housing. Remove the old filter cartridge, clean the housing, and install a new OEM DEF filter.

4. 4

   Inspect/Replace Components

   Inspect the wiring connectors to the DEF pump and pressure sensor. If the filter replacement does not resolve the low pressure, the DEF pressure sensor or the DEF supply pump module itself may have failed and will require replacement.

5. 5

   System Test & Code Clearing

   After installing new parts, clear the stored E4332.18 fault code. Turn on the machine and verify sensor outputs for DEF level, temperature, and pressure. Run a manual or automatic SCR system test to confirm the system builds pressure correctly and no new errors appear.