Case IH 19651 (DTC 229A) - ECU – DCU (Dosing Control Unit): DEF/AdBlue tank level sensor voltage too low / UREA Tank level error - short circuit low

The control module is receiving a voltage signal from the Diesel Exhaust Fluid (DEF) tank level sensor that falls below the acceptable minimum threshold. This condition is typically caused by a short circuit to a low voltage source (ground), an open circuit in the sensor wiring, or an internal failure of the DEF tank sending unit (DEF header).

• MAXXUM T4E
• 240 Series Axial-Flow Combines
• Magnum Series (180–380, 235–340 Series 4)
• Steiger 4WD Tractors (350–600 HP)
• Puma
• Maxxum
• Optum
• Farmall series

1. 1

   Verify the physical DEF/AdBlue tank fluid level (requires up to two minutes with key on to detect)

2. 2

   Inspect the DEF header unit, wiring harness, and connectors for signs of corrosion, moisture, or physical damage

3. 3

   Test the wiring harness between the DEF level sensor and the DCU for a short to ground or open circuit

4. 4

   Check for DEF contamination or crystallization that could damage the sending unit sensor

1. 1

   Power Down

   Turn off the machine and ensure the key is removed from the ignition.

2. 2

   Clear Simple Faults

   If the tank was empty, fill it with fresh, high-quality DEF. Turn the key to the ON position and wait at least two minutes to see if the system registers the fluid and clears the code.

3. 3

   Inspect Connections

   If the code persists, disconnect the DEF tank level sensor connector. Inspect the pins for corrosion, moisture, or pushed-out terminals. Clean with contact cleaner and reconnect.

4. 4

   Test the Circuit

   Use a multimeter to check the sensor's supply voltage and signal return circuits against the specifications in your service manual.

5. 5

   Replace the DEF Header

   If the wiring harness tests good but the sensor output remains out of range (shorted low), the DEF header unit has failed internally.

6. 6

   Removal

   Drain the DEF tank if required by your specific model's manual. Remove the mounting hardware/retaining ring for the DEF header unit, and carefully extract the faulty sensor assembly from the tank.

7. 7

   Installation

   Install the new DEF level sensor/header unit, ensuring the O-ring or gasket is properly seated to prevent leaks.

8. 8

   Finalize

   Reconnect the wiring harness, refill the DEF tank, and use a diagnostic scan tool to clear the stored fault codes. Run the machine to verify the SCR system is functioning normally and no power derate (SCR Inducement) is active.