Massey Ferguson 1761.03 – Engine Control Unit (ECU): DEF Tank Level Sender High Voltage

The Engine Control Unit (ECU) has detected that the voltage signal from the Diesel Exhaust Fluid (DEF) tank level sensor is above normal or out of range high. This typically indicates a short circuit to a 12V power source or an open circuit in the sensor wiring. This abnormal reading prevents the ECU from knowing the actual DEF level, which will trigger an emissions warning and eventually lead to an engine power derate.

• 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
• 7714S
• 7719S

1. 1

   Visually inspect the DEF tank to ensure it is not overfilled and verify the fluid quality.

2. 2

   Inspect the wiring harness leading to the DEF tank header for pinched wires, chafing, or disconnected plugs. Check the connector pins for corrosion or moisture.

3. 3

   Disconnect the DEF level sensor, turn the key ON, and use a multimeter to verify the sensor is receiving the correct reference voltage (typically 5V or 12V).

4. 4

   Test the signal wire for continuity to the ECU and ensure it is not shorted to a 12V power source.

5. 5

   If the wiring is intact, check for an internal disconnection within the DEF header or a physically stuck float inside the tank.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery master switch to prevent electrical spikes.

2. 2

   Clean the Area

   Thoroughly clean the top of the DEF tank and around the DEF header assembly to prevent dirt or debris from falling into the tank during removal.

3. 3

   Disconnect Lines

   Carefully unplug the electrical connector from the DEF header. Disconnect the DEF suction, return, and heated coolant lines (if equipped). Note: Be prepared to catch minor fluid spills.

4. 4

   Remove the Sensor

   Unscrew the retaining ring or mounting bolts holding the DEF header/level sensor assembly to the tank. Carefully pull the unit straight up and out of the tank.

5. 5

   Install New Part

   Insert the new DEF header assembly into the tank, ensuring the gasket/O-ring is properly seated to prevent leaks. Secure the retaining ring or bolts.

6. 6

   Reconnect

   Reattach all fluid lines and the electrical connector.

7. 7

   Clear Codes

   Reconnect the battery. Use a compatible diagnostic scan tool (such as WinEEM4 or an AGCO diagnostic tool) to clear the stored error log in the ECU.

8. 8

   Test

   Restart the ECU/tractor and verify that the DEF gauge reads accurately and the fault code does not return.