Massey Ferguson E4344.02 – Engine Control Unit (ECU): DEF Unit Internal Temperature Sensor Issue

The DEF supply module's temperature measurement module is not responding. This is typically caused by a defective internal temperature sensor, a damaged, shorted, or disconnected wiring harness, or a failed DEF supply module.

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

1. 1

   Perform a software reset by saving and erasing the error log, then cycle the key and test drive to see if the fault returns

2. 2

   Inspect the DEF supply module wiring harness for chafed wires, loose pins, or corrosion at the connector that plugs into the DEF pump unit

3. 3

   Verify component voltage and ground; if wiring is intact, the internal temperature sensor is defective and the module requires replacement

1. 1

   Turn off the tractor and disconnect the battery

   Ensure safety and prevent short circuits.

2. 2

   Locate the DEF Supply Module

   Typically mounted near the base of the DEF tank.

3. 3

   Clean the area

   Thoroughly clean the area around the module to prevent dirt or debris from entering the sensitive SCR system.

4. 4

   Disconnect the electrical harness

   Disconnect the electrical harness from the DEF supply module.

5. 5

   Disconnect fluid lines

   Disconnect the heated DEF supply and return lines. Note: Be careful with the quick connectors and O-rings, as nicks can cause air ingress and priming faults later.

6. 6

   Remove the module

   Unbolt and remove the defective DEF supply module.

7. 7

   Install the new module

   Install the new DEF supply module and securely reconnect the fluid lines and electrical harness.

8. 8

   Reconnect the battery

   Reconnect the battery.

9. 9

   Clear the fault code

   Use a diagnostic service tool (like WinEEM3s/WinEEM4s) to clear the E4344.02 fault code from the EEM.

10. 10

    Verify repair

    Run the machine to verify that the DEF system primes successfully and the code does not return.