Massey Ferguson E4344.12 – Engine Control Unit (ECU): DEF Unit Internal Temperature Sensor Issue

The sensor responsible for monitoring the temperature of the Diesel Exhaust Fluid (DEF / AdBlue) inside the DEF tank is sending an erratic, out-of-range, or missing signal.

• 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

1. 1

   Inspect the wiring harness and connector at the DEF tank header unit for chafed wires, broken pins, corrosion, or water ingress.

2. 2

   Ensure the tank has an adequate level of DEF and that it is not frozen solid. Use a DEF refractometer to verify the fluid is at the required 32.5% urea concentration.

3. 3

   Use a diagnostic scan tool to view the live data for the DEF tank temperature. If the reading is pegged at an extreme value (e.g., -40°C or +150°C) or fluctuates wildly while ambient temperature is stable, the internal sensor has failed.

1. 1

   Purge Cycle

   Turn off the tractor and wait at least 2 to 5 minutes before disconnecting the battery. The DEF system must complete its automatic purge cycle to pump fluid out of the lines and back into the tank.

2. 2

   Prep and Clean

   Locate the DEF tank. Thoroughly clean the top of the tank and the area around the DEF header unit. The SCR system is highly sensitive to contamination; no dirt or debris can be allowed to fall into the tank.

3. 3

   Disconnect

   Disconnect the electrical harness connector from the DEF header. Carefully disconnect the heated DEF supply and return lines (be prepared to catch minor drips).

4. 4

   Removal

   Remove the mounting bolts or the retaining ring securing the DEF header assembly to the tank. Carefully pull the old sensor assembly straight up and out of the tank.

5. 5

   Installation

   Insert the new DEF sensor assembly using a new mounting O-ring/seal to prevent moisture and dust ingress. Secure the bolts/ring to the manufacturer's torque specification.

6. 6

   Reconnect

   Reattach the DEF fluid lines (ensuring the quick connectors click into place) and plug in the electrical harness.

7. 7

   Clear Codes

   Reconnect the battery. Turn the key to the ON position and use a diagnostic tool to clear the E4344.12 fault code. Start the engine and run it at a high idle to verify the code does not return and the system registers the correct temperature.