Case IH 19523 – Engine Control Unit (ECU): DEF/AdBlue tank temperature failure

This fault code indicates that the temperature sensor inside the Diesel Exhaust Fluid (DEF) tank is reporting an implausible value, an abnormal rate of change, or a value outside acceptable limits.

• Tier 4b
• N-Series Tractor Loader Backhoes (TLBs)
• Maxxum series tractors
• Puma series tractors
• Optum series tractors
• Magnum series tractors
• Steiger series tractors
• Axial-Flow combines
• Skid steers
• Compact track loaders
• TV620B
• SR270B

1. 1

   Check the DEF tank header wiring harness and connectors for physical damage, rodent damage, corrosion, or loose pins.

2. 2

   Test the sensor wiring for a short to ground, short to battery, or an open circuit between the DEF tank header connector and the ECU.

3. 3

   Verify that the engine coolant lines running to the DEF tank heater valve are getting hot and that the DEF tank maximum defrost time hasn't simply been exceeded due to extreme cold.

4. 4

   Ensure the DEF tank is filled with clean, unexpired, API-certified DEF, as degraded fluid can sometimes cause erratic sensor readings.

1. 1

   Preparation

   Stop the engine, turn off the battery disconnect switch, and allow the machine and exhaust system to cool completely.

2. 2

   Clean the Area

   Thoroughly clean the top of the DEF tank around the header unit to prevent dirt or debris from falling into the tank.

3. 3

   Drain Fluid

   Drain the DEF tank if you are replacing the entire header unit to prevent spills.

4. 4

   Disconnect Lines

   Carefully disconnect the electrical connector and the coolant/heating lines attached to the DEF tank header. Cap the coolant lines to prevent excessive coolant loss.

5. 5

   Remove the Header

   Unscrew the large locking ring or remove the mounting bolts securing the DEF tank header to the tank.

6. 6

   Extract the Unit

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

7. 7

   Install New Part

   Insert the new DEF header unit, ensuring the rubber O-ring/seal is properly seated to prevent leaks. Tighten the locking ring to OEM spec.

8. 8

   Reconnect

   Reconnect the coolant lines and the electrical connector.

9. 9

   Refill and Clear

   Refill the tank with fresh DEF. Turn on the battery, connect a diagnostic tool (such as the Case IH Electronic Service Tool - EST), and clear the inactive fault codes. Run the machine to verify the code does not return.