Case IH 19106 (DTC 759A) - ECU – Engine ECU or DCU: DEF/AdBlue tank heater actuator short circuit to ground failure.

The Selective Catalytic Reduction (SCR) system uses hot engine coolant to thaw Diesel Exhaust Fluid (DEF) inside the tank during cold weather. The flow of this coolant is controlled by a solenoid-actuated valve known as the DEF tank heater valve (or coolant control valve). This fault code indicates that the control module has detected a short circuit to ground on the electrical circuit that controls this valve's actuator.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Steiger (e.g., 535, 580)
• Magnum (e.g., 235–340 Series 4)
• Puma
• Maxxum
• Farmall A/C series (110A, 120A, 130A, 140A, 120C)
• CX Series (e.g., CX140E, CX170E, CX220E, CX260E)
• Farmlift Series (e.g., 737 Stage IV)

1. 1

   Inspect the wiring harness leading to the DEF tank heater coolant valve solenoid. Look for chafing, bare wires touching the chassis, or melted insulation that would cause a short to ground.

2. 2

   Disconnect the valve and check the resistance across the heating valve solenoid pins. An internal short in the solenoid will require replacing the valve.

3. 3

   Verify that the DEF tank hoses are installed correctly. Official dealer documentation notes that if hoses are routed incorrectly (e.g., the DEF heater line with the 'red' band must connect to the top tube running to the front of the engine head on Fargo-built tractors), hot water can circulate continuously, overheating the tank and potentially damaging the valve.

4. 4

   Ensure the Coolant Control Valve (CCV) is not physically stuck open or leaking. Check if the coolant lines are warm to the level unit when the engine is warm but the ambient temperature does not require DEF heating.

1. 1

   Preparation

   Turn off the machine, disconnect the battery, and allow the engine and coolant to cool completely.

2. 2

   Drain Coolant

   Drain the engine coolant to a level below the heater valve, or use hose pinch-off pliers on the coolant lines leading to and from the valve to prevent excessive fluid loss.

3. 3

   Disconnect Electricals

   Unplug the electrical connector from the DEF tank heater control valve.

4. 4

   Remove Hoses

   Loosen the hose clamps and disconnect the engine coolant hoses from the valve.

5. 5

   Remove Valve

   Remove the retaining bolts securing the coolant control valve support bracket to the machine.

6. 6

   Install New Valve

   Mount the new coolant control valve assembly and install the retaining bolts. (For example, on Farmall 140A models, torque the M14 retaining bolts to 99 - 108 N·m / 73 - 80 lb ft).

7. 7

   Reassemble

   Reconnect the coolant hoses and tighten the clamps. Reconnect the electrical connector.

8. 8

   Refill & Clear

   Refill the engine coolant, bleed the cooling system of air, and use a diagnostic tool to clear the 19106 / 759A fault code. Run the machine to verify there are no coolant leaks and the code does not return.