Case IH F-3363-03 - ECU – Engine Control Unit (ECU): DEF tank heater coolant valve solenoid short circuit to HIGH SOURCE

The DEF (Diesel Exhaust Fluid) system uses engine coolant to thaw frozen AdBlue/DEF in cold weather. The flow of this hot coolant is regulated by the DEF tank heater coolant control valve (actuator). This code indicates that the monitoring system has detected a short circuit to the battery (high voltage source) on the power stage of this solenoid valve.

• MAGNUM AFS Connect
• Steiger (350-600, 535, 580)
• Magnum (235-340 Series 4)
• Puma
• Maxxum
• Farmall (110A-140A)
• Axial-Flow 7120
• Axial-Flow 7240
• Axial-Flow 8240
• Axial-Flow 9240
• CX220E
• CX260E
• 621F
• 721F

1. 1

   Stop the engine and let the machine and coolant cool down completely before starting work.

2. 2

   Check the wiring harness and connectors leading to the DEF tank heater coolant valve for physical damage, rubbing, or melted insulation that could cause a short to a high-voltage source.

3. 3

   Inspect the connector pins for debris, water intrusion, or loose machine grounds (earths).

4. 4

   Test the solenoid valve wiring to confirm if the short is in the harness (shorted to high source) or if the solenoid valve itself has failed internally.

5. 5

   If available, plug the harness into a known-good dosing/coolant valve to see if the fault code changes from active to inactive, confirming the original valve is defective.

6. 6

   Ensure the Coolant Control Valve (CCV) is not mechanically stuck open or leaking coolant.

1. 1

   Safely shut down the machine, turn off battery power, and allow the engine coolant to cool.

2. 2

   Locate the DEF/AdBlue heating control valve (Coolant Control Valve).

   It is typically mounted on a support bracket near the engine block or inline with the coolant hoses routing to the DEF tank.

3. 3

   Disconnect the electrical connector from the DEF tank heater valve.

4. 4

   If the diagnostic checks proved the wiring harness is shorted to the battery, repair or replace the damaged section of the wiring harness.

5. 5

   If the solenoid itself is internally shorted, proceed with replacing the valve.

   Pinch off the coolant lines or drain the engine coolant to prevent spills. Remove the retaining bolts (e.g., M14 or M6 bolts depending on the model) securing the coolant control valve or its support bracket to the machine. Disconnect the coolant hoses from the defective valve. Install the new DEF tank heater coolant control valve and torque the retaining bolts to factory specifications (e.g., 99 - 108 N·m / 73 - 80 lb ft for certain Farmall brackets). Reconnect the coolant hoses and the electrical connector.

6. 6

   Refill and bleed the engine coolant system if any fluid was lost.

7. 7

   Turn on the machine, clear the fault codes using a diagnostic tool, and run the engine to verify the code does not return and that there are no coolant leaks.