Case IH 19175 – DCU (Dosing Control Unit) or Engine ECU: DEF/AdBlue tank level sensor indicates too high fill level.

The DEF (Diesel Exhaust Fluid) level sensor reports a fluid level that exceeds the maximum plausible threshold. This can be caused by physically overfilling the tank into the filler neck, DEF fluid freezing and expanding, a short circuit in the sensor wiring, or an internal failure of the DEF header unit's level sensor.

• Tier 4b
• Steiger
• Magnum
• Puma
• Maxxum
• Farmall
• Axial-Flow series
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 9230
• Case loaders
• Case skid steers
• Case CTLs

1. 1

   Check physical fluid level: Visually inspect the DEF tank. If it was recently topped off to the very brim of the filler neck, drain a small amount of fluid to bring it down to the normal 'Full' line.

2. 2

   Check for freezing: If operating in freezing temperatures (below 12°F / -11°C), allow the machine to thaw in a heated shop to see if the code clears. Frozen DEF expands and can push the level sensor up, triggering a false 'too high' reading.

3. 3

   Inspect wiring and connectors: Check the electrical harness plugging into the DEF header unit on top of the tank. Look for corrosion, moisture intrusion, or bent pins that could cause a short circuit.

4. 4

   Live data verification: Use the CNH Electronic Service Tool (EST) to monitor the live DEF level voltage or percentage. If the tank is half empty but the software reads 100%+, the sensor itself has failed internally.

1. 1

   Preparation

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

2. 2

   Access the DEF tank

   Locate the DEF header unit mounted to the top of the DEF tank. Clean the area around the mounting flange thoroughly to prevent dirt or debris from falling into the tank when the unit is removed.

3. 3

   Disconnect lines

   Disconnect the electrical connector from the header. Next, pinch off and disconnect the engine coolant lines that run to the header (be prepared with a rag to catch a small amount of spilled coolant).

4. 4

   Remove the header

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

5. 5

   Install the new unit

   Insert the new DEF header unit into the tank, ensuring the new rubber flange seal/O-ring is seated correctly to prevent leaks.

6. 6

   Reassembly

   Tighten the mounting bolts/ring. Reconnect the coolant lines and the electrical harness.

7. 7

   Clear codes

   Reconnect the battery. Turn the ignition on and use the CNH EST diagnostic tool to clear the 19175 fault code and verify that the tank level is now reading accurately.