Case IH 19105 (DTC 879A) - ECU – Engine Control Unit (ECU): DEF/AdBlue tank heater ECU driver over temperature failure.

The Engine Control Unit (ECU) has detected that the internal driver circuit responsible for commanding the DEF/AdBlue tank heater actuator (the coolant control valve) has exceeded its safe operating temperature. This typically occurs when the DEF tank heater control valve draws excessive current, shorts out, or mechanically sticks open. When stuck open, hot engine coolant circulates continuously through the DEF tank, physically overheating the system and overworking the ECU driver.

• MAXXUM T4E
• 240 Series Axial-Flow® Combines
• Steiger tractors
• Magnum tractors

1. 1

   Check the DEF Tank Heating Valve: Inspect the coolant control valve for the DEF tank to ensure it is operating normally and is not mechanically stuck open.

2. 2

   Verify Coolant Hose Routing: Inspect the DEF tank heater hoses to ensure they are installed correctly (e.g., red band connected to the top tube running to the front of the engine head) to prevent continuous hot water circulation.

3. 3

   Inspect Wiring and Connectors: Check the wiring harness between the ECU and the DEF tank heater control valve for melted insulation, corrosion, or a short circuit.

1. 1

   Cool Down and Prep

   Turn off the machine and allow the engine and engine coolant to cool completely to prevent burn injuries.

2. 2

   Locate the Valve

   Locate the DEF tank heater control valve, which regulates coolant flow to the DEF tank.

3. 3

   Isolate the Coolant Lines

   Clamp off the DEF tank heater hoses and cab heater hoses at the rear of the engine/valve to prevent excessive coolant loss.

4. 4

   Disconnect Lines

   Loosen the hose clamps and disconnect the DEF tank heater hoses from the valve. Cap and plug all openings immediately to prevent fluid loss or system contamination.

5. 5

   Remove the Valve

   Disconnect the electrical connector from the DEF tank heater control valve and unbolt the valve from its mounting bracket.

6. 6

   Install the New Valve

   Mount the replacement DEF tank heater control valve.

7. 7

   Reconnect Hoses

   Reconnect the coolant hoses. Crucial step: Ensure the hoses are routed correctly (e.g., matching the red-banded hose to the correct upper port) so the valve is not damaged by reverse flow.

8. 8

   Reconnect Wiring

   Plug in the electrical connector.

9. 9

   Clear Codes

   Use a certified diagnostic tool to erase fault code 19105 (DTC 879A).

10. 10

    Test Operation

    Start the engine, allow it to reach operating temperature, and verify that the DEF tank temperature remains stable and the fault code does not return.