Massey Ferguson 3515.03 – Engine Control Unit (ECU): DEF Tank Temp Sensor Voltage High (ECU)

The controller is detecting an open circuit, a short to power, or an internal disconnection within the Diesel Exhaust Fluid (DEF) tank temperature sensor circuit.

• 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

   Visual Inspection: Check the main wiring harness connecting the ECU to the DEF tank header for physical damage, rubbing, or melted wires.

2. 2

   Connector Check: Disconnect the DEF tank header connector. Inspect the pins for corrosion, moisture, or pushed-back terminals.

3. 3

   Circuit Testing: Use a multimeter to check for an open circuit or a short to power on the temperature sensor signal wire.

4. 4

   Component Verification: The fault is highly likely to be an internal disconnection within the DEF header itself. If the wiring harness tests good (continuity to the ECU is intact and no shorts are present), the DEF sensor/header unit has failed internally.

1. 1

   Turn off the machine and disconnect the battery to prevent electrical spikes.

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the DEF tank and thoroughly clean the area around the top of the DEF header to prevent dirt from falling into the tank.

   Locate the DEF tank and thoroughly clean the area around the top of the DEF header to prevent dirt from falling into the tank.

3. 3

   Disconnect the electrical connector from the DEF header assembly.

   Disconnect the electrical connector from the DEF header assembly.

4. 4

   Disconnect the DEF fluid lines (supply and return) from the header.

   Disconnect the DEF fluid lines (supply and return) from the header. Caution: DEF fluid can be corrosive; clean up any spills immediately with warm water.

5. 5

   Unbolt or unscrew the locking ring securing the DEF header to the tank.

   Unbolt or unscrew the locking ring securing the DEF header to the tank.

6. 6

   Carefully extract the old DEF header assembly from the tank.

   Carefully extract the old DEF header assembly from the tank.

7. 7

   Install the new DEF sensor/header assembly, ensuring the O-ring/gasket is properly seated to prevent leaks.

   Install the new DEF sensor/header assembly, ensuring the O-ring/gasket is properly seated to prevent leaks.

8. 8

   Secure the locking ring, reconnect the fluid lines, and plug in the electrical connector.

   Secure the locking ring, reconnect the fluid lines, and plug in the electrical connector.

9. 9

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool to clear the 003515.03 fault code from the ECU.

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool to clear the 003515.03 fault code from the ECU.