Case IH 19650 (F-1761-03) – DCU (Dosing Control Unit) or Engine ECU: DEF/AdBlue tank level sensor voltage too high

The signal voltage returning from the DEF tank level sensor to the controller is above the normal operating range, which almost always points to an open circuit (a broken wire, disconnected plug, or internally failed sensor) or a short to a high-voltage source.

• VESTRUM CVX
• Magnum
• Steiger
• Puma
• Optum
• Maxxum
• Axial-Flow Combines 240 Series (7240, 8240, 9240)
• Axial-Flow Combines Tier 4 (5130, 6130, 7130, 7230, 8230, 9230)

1. 1

   Inspect the wiring harness and the electrical connector at the top of the DEF tank header for severe corrosion, pushed-out pins, or rubbed-through wires.

2. 2

   Disconnect the sensor and use a multimeter to check for continuity between the DEF header connector and the DCU/ECU to rule out a broken harness.

3. 3

   Hook up a diagnostic scan tool (such as the CNH Electronic Service Tool) and monitor the live voltage of the DEF level sensor. A steady 5V (or system reference voltage) with no fluctuation indicates an open circuit.

4. 4

   Check if the DEF fluid is frozen or if crystallized DEF has physically damaged the sensor probe inside the tank.

1. 1

   Prep the Machine

   Turn off the equipment, remove the key, and disconnect the battery to prevent electrical shorts.

2. 2

   Clean the Area

   Thoroughly clean the top of the DEF tank around the header flange. DEF systems are highly sensitive to contamination, so no debris can be allowed to fall into the tank.

3. 3

   Disconnect Lines

   Carefully unplug the electrical connector from the DEF header. Disconnect the DEF supply and return lines (be prepared for minor fluid spillage and wipe it up immediately).

4. 4

   Remove the Header

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

5. 5

   Install the New Part

   Insert the new DEF header assembly into the tank, ensuring the new rubber flange seal/gasket is seated correctly to prevent leaks.

6. 6

   Reassemble

   Tighten the mounting bolts, reconnect the DEF fluid lines, and plug in the electrical connector.

7. 7

   Clear Codes

   Reconnect the battery. Turn the ignition on and use a diagnostic scan tool to clear the 19650 / F-1761-03 fault code. Verify that the live DEF level is now reading accurately on the cab display.