Massey Ferguson 3515.17 – Engine Control Unit (ECU): DEF Tank Temp Sensor Error Low Temperature

The system is receiving a voltage signal from the DEF tank temperature sensor that translates to an abnormally low temperature. This is usually caused by an electrical fault (open circuit, high resistance, or failed thermistor) or a mechanical/heater fault (DEF fluid is frozen because the heating system failed).

• 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
• 6700S
• 7614 through 7626
• 7714 through 7726 (including 'S' variants)

1. 1

   Check Ambient Conditions & Heater: If operating in freezing temperatures, verify that the DEF tank heater coolant valve is opening and that the heated lines are functioning.

2. 2

   Visual Inspection: Inspect the wiring harness and the electrical connector at the top of the DEF tank header for rubbed wires, corrosion, or moisture.

3. 3

   Test the Sensor: Use a multimeter to check the resistance of the temperature sensor pins at the DEF header (an infinite reading indicates an internal open circuit).

4. 4

   Check for Contamination: Ensure the DEF tank cap is sealed and the fluid is free of crystallization or diesel contamination.

1. 1

   Clean the Area

   Thoroughly clean the top of the DEF tank and the area around the header. Treat the tank neck like a fuel filler on a jet.

2. 2

   Disconnect Power

   Turn off the tractor and disconnect the battery to prevent short circuits or ECU spikes.

3. 3

   Disconnect Lines

   Carefully unplug the electrical harness connector from the DEF header. Disconnect the DEF supply and return lines (usually quick-connect fittings) and cap them immediately to prevent contamination.

4. 4

   Remove the Header

   Unscrew the locking ring or remove the mounting bolts securing the header assembly to the DEF tank.

5. 5

   Extract

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

6. 6

   Install New Part

   Insert the new DEF tank header assembly, ensuring the new rubber O-ring/gasket is properly seated to prevent leaks and air ingress.

7. 7

   Reassemble

   Tighten the locking ring/bolts. Reconnect the DEF fluid lines and the electrical harness.

8. 8

   Clear Codes

   Reconnect the battery. Use an AGCO diagnostic tool (or equivalent scanner) to clear the 003515.17 fault code from the ECU. Run the tractor to confirm the code does not return.