Case IH 19651 (F-1761-04) – DCU (Dosing Control Unit) or Engine ECU: DEF/AdBlue tank level sensor voltage too low

The control module is receiving a voltage signal from the DEF tank level sensor that is below the acceptable minimum threshold, indicating either a direct short to ground in the wiring or an internal short within the sensor itself.

• VESTRUM CVX
• Steiger Series 350
• Steiger Series 400
• Steiger Series 450
• Steiger Series 500
• Steiger Series 550
• Steiger Series 600
• Magnum Series 235 - 340 (Series 4)
• Puma Series
• Combines (9900 series)

1. 1

   Check the DEF fluid level manually to ensure the tank is not completely empty.

2. 2

   Inspect the wiring harness connecting the DEF tank level sensor to the DCU/ECU for chafing, melted wires, or corrosion at the connector pins.

3. 3

   Disconnect the sensor and use a multimeter to check the harness for a short to ground (short circuit to a low voltage source).

4. 4

   Verify that the CAN bus communication lines are intact and not shorted.

5. 5

   If the wiring harness tests fine (no shorts to ground and proper reference voltage is present), conclude that the internal circuitry of the DEF level sensor has failed.

1. 1

   Turn off the machine, remove the key, and disconnect the battery

   Ensure safety while working on the electrical and emissions systems.

2. 2

   Locate the DEF tank

   The level sensor is typically integrated into the DEF Head Unit (or header assembly) which drops into the top of the tank.

3. 3

   Thoroughly clean the area around the top of the DEF tank and the sensor flange

   DEF systems are highly sensitive to contamination; dirt entering the tank will destroy the DEF dosing pump.

4. 4

   Disconnect the electrical connector and the DEF fluid lines

   Disconnect from the top of the header unit.

5. 5

   Remove the mounting bolts or retaining ring

   Remove the hardware holding the DEF header unit in place.

6. 6

   Carefully pull the old DEF level sensor/header unit out of the tank

7. 7

   Install the new DEF level sensor assembly

   Ensure the gasket/O-ring is properly seated to prevent leaks and contamination.

8. 8

   Reinstall the retaining ring or bolts, and reconnect the DEF fluid lines and electrical harness

9. 9

   Reconnect the battery

10. 10

    Connect an Electronic Service Tool (EST) or compatible diagnostic scanner

    Clear the 19651 fault code.

11. 11

    Turn the key on and verify that the DEF level registers correctly

    Verify on the cab display and ensure the code does not return.