Massey Ferguson 3519.04 – Engine Control Unit (ECU) / EEM: DEF Tank Temperature Sensor Issue

The DEF tank temperature sensor's signal voltage is below normal or shorted to ground, indicating an implausible temperature reading from the Diesel Exhaust Fluid (DEF) tank.

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626

1. 1

   Inspect the wiring harness leading to the DEF tank header for chafing, melting, or pinch points that could cause a short to ground.

2. 2

   Disconnect the plug at the DEF tank header and check for loose contacts, pushed-out pins, or moisture/corrosion inside the connector.

3. 3

   Use a multimeter to test the sensor wiring back to the ECU for continuity and to ensure the signal wire is not shorted to the chassis ground.

4. 4

   If the wiring harness tests good, the internal temperature sensor inside the DEF header unit is defective and shorted internally and must be replaced.

1. 1

   Prep the Area

   Turn off the tractor and disconnect the battery. Thoroughly clean the top of the DEF tank around the header. Note: The DEF system is highly sensitive to contamination; treat the area like a jet fuel filler to prevent dirt from entering the tank.

2. 2

   Disconnect Lines

   Carefully disconnect the electrical connector and the DEF supply/return lines from the top of the header. Cap the lines immediately to prevent crystallization or contamination.

3. 3

   Remove the Header

   Unscrew the locking ring or unbolt the retaining hardware holding the DEF header to the tank.

4. 4

   Extract the Unit

   Carefully pull the old DEF header assembly straight up and out of the tank.

5. 5

   Install the New Part

   Insert the new DEF header assembly, ensuring the rubber O-ring/gasket is seated properly to prevent leaks and keep out dust/moisture.

6. 6

   Reassembly

   Secure the locking ring/bolts. Reconnect the DEF fluid lines (ensuring quick connectors click into place) and plug in the electrical harness.

7. 7

   Clear Codes

   Reconnect the battery. You will need to use a diagnostic service tool (such as AGCO EDT or WinEEM3s) to save the error log and then erase the active fault code to restore full engine power.