Case IH 19650 – DCU (Dosing Control Unit): DEF/AdBlue tank level sensor voltage too high

The control module is receiving a voltage signal from the Diesel Exhaust Fluid (DEF) tank level sensor that exceeds the maximum normal operating range, typically caused by a short circuit to a high voltage source in the wiring harness or an internal short/failure within the DEF level sensor itself.

• Tier 4b
• Tier 4a
• Stage V
• Magnum (235–340 Series 4)
• Steiger (350–600)
• Puma
• Maxxum 150 Multicontroller
• Farmall 90C
• Farmall 100C
• 240 Series Axial-Flow Combines

1. 1

   Visually inspect the wiring harness running from the DEF tank header to the DCU for chafed wires, melted insulation, or pinch points that could cause a short to power.

2. 2

   Disconnect the DEF tank level sensor and inspect the pins on both the sensor side and the harness side for corrosion, moisture, DEF fluid intrusion, or bent pins.

3. 3

   With the sensor disconnected and the key ON, probe the signal wire on the harness side. If high voltage is still present, the wiring harness is shorted to a power wire. If the voltage drops to baseline/zero, the short is internal to the DEF tank level sensor.

1. 1

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

2. 2

   Clean the area around the top of the DEF tank thoroughly to prevent dirt or debris from falling into the tank.

3. 3

   Disconnect the electrical connector from the DEF header/level sensor.

4. 4

   Disconnect the DEF suction and return lines from the header.

   Be prepared to catch minor fluid spillage.

5. 5

   Remove the mounting bolts or unscrew the locking ring securing the DEF header to the tank.

6. 6

   Carefully pull the old DEF header/sensor assembly straight up and out of the tank.

7. 7

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

8. 8

   Reinstall the locking ring or mounting bolts.

9. 9

   Reconnect the DEF fluid lines and the electrical connector.

10. 10

    Reconnect the battery, turn the key ON, and use a diagnostic scan tool to clear the inactive 19650 fault code from the DCU.

    Verify the DEF gauge on the dash now reads the correct fluid level.