Massey Ferguson 3031.03 – Engine Control Unit (ECU): Issue With The Temperature Of The DEF Tank Temperature Sensor

DEF Tank Fluid Temperature Signal is Out of Range High or the Voltage is Above Normal. This typically means the Engine Control Unit (ECU) has detected a short circuit to a high voltage source (e.g., a short to 12V) or an open circuit in the DEF tank temperature sensor wiring.

• 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

1. 1

   Visual Inspection: Inspect the DEF tank and sensor housing for physical damage, cracks, or heavy corrosion.

2. 2

   Harness & Connector Check: Disconnect the DEF sensor wiring harness. Inspect the pins and connectors for water ingress, corrosion, or bent pins.

3. 3

   Circuit Testing: Using a multimeter, check the sensor wiring harness for an open circuit or a short circuit to 12V power.

4. 4

   Fluid Verification: Ensure the DEF tank is adequately filled and that the fluid is not frozen solid.

5. 5

   Clear and Retest: Clear the fault codes, run the engine on high idle for 2 minutes, cycle the key off for 15 seconds, and restart. If the code returns as active, the sensor itself has likely failed internally.

1. 1

   Preparation

   Turn off the engine, remove the key, and allow the DEF system to complete its purge cycle (wait at least 2-5 minutes after key-off).

2. 2

   Access the Sensor

   Locate the DEF tank sending unit assembly on top of the DEF tank.

3. 3

   Disconnect

   Unplug the electrical connector to the DEF sensor. Disconnect the DEF suction, return, and coolant heating lines (be prepared to catch minor coolant/DEF spillage).

4. 4

   Removal

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

5. 5

   Installation

   Insert the new DEF sensor assembly into the tank, ensuring the gasket/O-ring is properly seated to prevent contamination. Secure the mounting bolts/ring.

6. 6

   Reconnection

   Reconnect the DEF fluid lines, coolant lines, and the electrical harness.

7. 7

   Verification

   Turn the key on, use a diagnostic tool to clear the ECU fault codes, and run the engine to verify the repair and ensure there are no leaks.