Massey Ferguson 4344.12 – Engine ECU: DEF Unit Internal Temperature Sensor Issue (ECU)

The engine control unit has lost communication with or is receiving an invalid signal from the temperature sensor located inside the Diesel Exhaust Fluid (DEF) supply module.

• 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

1. 1

   Clear the Code: Save the error log and then erase it using a diagnostic tool, then restart the ECU/tractor to see if the fault returns.

2. 2

   Inspect Wiring: Check the wiring harness and connectors leading to the DEF supply module for chafed wires, corrosion in the connector pins, or open circuits.

3. 3

   Verify Module Failure: If the wiring is intact and the ECU still reports that the temperature measurement module is not responding, the internal sensor has failed.

1. 1

   Turn off the tractor and disconnect the battery to ensure the ECU is powered down.

2. 2

   Locate the DEF supply module (pump) assembly near the DEF tank.

3. 3

   Thoroughly clean the area around the module to prevent dirt from entering the DEF lines.

4. 4

   Disconnect the electrical harness connector from the DEF supply module.

5. 5

   Disconnect the DEF supply and return lines.

   Have a catch pan ready, as some DEF fluid will leak out.

6. 6

   Unbolt and remove the defective DEF supply module.

7. 7

   Install the new DEF supply module and torque the mounting bolts to OEM spec.

8. 8

   Reconnect the DEF fluid lines, ensuring they click securely into place.

9. 9

   Reconnect the electrical harness.

10. 10

    Reconnect the battery, turn the key on, and use a diagnostic tool to clear the 004344.12 fault code.

11. 11

    Run the tractor to verify the code does not return and that the DEF system primes successfully without leaks.