Massey Ferguson 3515.15 – Engine Control Unit (ECU): DEF Tank Temp Sensor Error High Temperature

The temperature sensor located inside the Diesel Exhaust Fluid (DEF) tank is reporting a value that is above the normal operating range (often reading an impossible value like 80°C or 125°C due to an internal short). When this code is active, the engine will eventually enter a derate mode to comply with emissions regulations.

• 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
• 7714S
• 7719S

1. 1

   Connect a diagnostic tool and view live data for the DEF Tank Temperature; an impossibly high temperature on a cold tractor indicates an internal sensor failure.

2. 2

   Inspect the 4-pin connector (Deutsch DT04) at the top of the DEF tank header for corrosion, moisture intrusion, or chafed wires causing a short circuit.

3. 3

   Check the DEF heater coolant control valve; if stuck open, it will continuously boil the DEF fluid, causing a legitimate high-temperature reading and potential sensor damage.

4. 4

   Check for companion codes such as SPN 3031, SPN 3516, or SPN 1761, which usually confirm a total failure of the DEF header assembly.

1. 1

   Clean the Area

   Thoroughly clean the top of the DEF tank around the header unit. The SCR system is highly sensitive to contamination; dirt entering the tank will destroy the DEF injector.

2. 2

   Disconnect Power

   Turn off the battery disconnect switch.

3. 3

   Disconnect Lines

   Disconnect the electrical harness from the DEF header. Carefully disconnect the DEF supply and return lines (these usually utilize quick-connect fittings with O-rings).

4. 4

   Remove the Header

   Unscrew the locking ring or remove the mounting bolts securing the DEF header to the tank. Carefully pull the header assembly straight up and out of the tank.

5. 5

   Install the New Unit

   Insert the new DEF header assembly, ensuring the new rubber sealing gasket/O-ring is properly seated to prevent leaks and contamination. Secure the locking ring/bolts.

6. 6

   Reconnect

   Reconnect the DEF fluid lines and the electrical connector.

7. 7

   Refill and Clear

   Top off the tank with fresh, clean DEF. Turn on the battery, connect your diagnostic tool, and clear the ECU fault codes. Run the engine to ensure the derate is lifted and no leaks are present.