Case IH F-1761-16 - ECU – Engine Control Unit (ECU): DEF/AdBlue tank level sensor voltage too high

The sensor measuring the Diesel Exhaust Fluid (DEF) level is sending a voltage signal back to the control module that exceeds the maximum calibrated threshold.

• MAGNUM AFS Connect
• Magnum series (250, 290, 340, 380)
• Steiger series
• Farmall (90C, 110U)
• Maxxum
• Puma
• Axial-Flow series (5130, 7140, 8250, 9240)
• Patriot sprayers
• Case construction equipment

1. 1

   Visually inspect the DEF tank to ensure it is not physically overfilled up into the filler neck (overfilled tank cause).

2. 2

   Inspect the wiring harness connecting the DEF header to the ECU for chafed wires, melted insulation, or a short-to-power (wiring fault cause).

3. 3

   Disconnect the sensor and check the pins for corrosion or DEF crystal buildup, which is highly corrosive to wiring.

4. 4

   Use a multimeter to check the reference voltage at the connector. If the wiring is good, the fault is likely internal to the sensor.

5. 5

   Hook up the Case IH Electronic Service Tool (EST) to monitor the live DEF level voltage data. If it reads a constant maximum voltage (e.g., 5V) even when the tank is half empty, the sending unit has failed (internal sensor failure cause).

1. 1

   Prep the machine

   Turn off the machine, disconnect the battery, and thoroughly clean the area around the top of the DEF tank to prevent dirt or debris from falling into the tank.

2. 2

   Drain DEF fluid

   Drain the DEF tank below the level of the header unit to prevent spills.

3. 3

   Disconnect lines and connectors

   Carefully disconnect the electrical connector and the DEF supply/return lines from the top of the DEF header. Cap the lines immediately to prevent contamination, as DEF degrades plastics and corrodes metal.

4. 4

   Remove the DEF header

   Unscrew the locking ring or mounting bolts securing the DEF sender unit to the tank flange. Carefully pull the old unit straight up and out of the tank.

5. 5

   Install the new DEF header

   Insert the new DEF header assembly into the tank, ensuring the rubber gasket/O-ring is properly seated. Tighten the locking ring/bolts to OEM torque specs.

6. 6

   Reconnect lines

   Reattach the DEF fluid lines and the electrical connector.

7. 7

   Refill and clear codes

   Refill the tank with fresh, high-quality DEF. Reconnect the battery, turn the key on, and use the Case IH EST to clear the F-1761-16 fault code. Run the engine to verify the dashboard DEF gauge reads accurately and no codes return.