Massey Ferguson E4344.03 – Engine Control Unit (ECU): DEF Unit Internal Temperature Sensor Issue

The temperature sensor located inside the Diesel Exhaust Fluid (DEF) supply module (also known as the DEF pump or head module) is failing to send a valid signal, which will trigger a warning lamp and eventually cause an engine derate.

• 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 7716S
• MF 7718
• MF 7718S
• MF 7719
• MF 7720
• MF 7720S
• MF 7722
• MF 7722S
• MF 7724
• MF 7724S
• MF 7726
• MF 7726S

1. 1

   Clear the error log using a diagnostic tool, restart the ECU, and check if the fault returns to rule out a transient CAN message error.

2. 2

   Inspect the wiring harness leading to the DEF supply module for chafed wires, kinks, or rub points.

3. 3

   Disconnect the DEF supply module electrical connector and inspect for corrosion, moisture, or bent pins. Clean contacts and reseat securely.

4. 4

   If wiring is intact and the fault immediately returns, the internal temperature sensor is defective, requiring module replacement.

1. 1

   Preparation

   Turn off the tractor, remove the key, and disconnect the battery to prevent electrical shorts. Ensure the work area is spotless; the DEF system is highly sensitive to dirt and diesel contamination.

2. 2

   Locate the Module

   Locate the DEF supply module (pump/head module), which is typically mounted directly on or adjacent to the DEF/AdBlue tank.

3. 3

   Disconnect Lines

   Carefully disconnect the heated DEF supply and return lines. Cap the lines immediately to prevent air ingress, dirt contamination, or urea crystallization.

4. 4

   Disconnect Electricals

   Unplug the main electrical harness connector from the module.

5. 5

   Remove the Module

   Unbolt the DEF supply module from its mounting bracket or tank housing.

6. 6

   Install the New Module

   Mount the replacement DEF supply module. Reconnect the heated lines, ensuring the quick connectors and O-rings are fully seated and undamaged.

7. 7

   Reconnect Electricals

   Plug the electrical harness back into the new module.

8. 8

   Finalize

   Reconnect the battery. Use a diagnostic service tool to clear the E4344.03 fault code from the EEM. Turn the key on to prime the system and check for leaks before starting the engine.