Case IH F-3363-06 - ECU – Engine Control Unit (ECU) or Dosing Control Unit (DCU) / SCR Control Module: DEF/AdBlue tank heater ECU driver over temperature failure

The internal driver circuit inside the control module that provides the ground/power stage to the DEF tank heater coolant valve has detected an over-temperature condition. This is almost always caused by excessive current draw, which typically stems from a short circuit to ground in the wiring harness or an internally shorted DEF tank heater coolant valve solenoid.

• MAGNUM AFS Connect
• Steiger 535
• Steiger 580
• Magnum
• Maxxum
• Puma
• Optum
• Axial-Flow 240 Series
• Axial-Flow CR/CX Series

1. 1

   Check the DEF tank heater coolant valve solenoid resistance using a multimeter across the pins; an out-of-spec or near-zero reading indicates an internal short.

2. 2

   Inspect the wiring harness from the DEF tank heater coolant valve back to the ECU/DCU for chafing, pinched wires, or a short to ground on the low-side power stage wire.

3. 3

   Check ECU connector pins for damage, corrosion, or pins that have been pushed back, which can cause ground faults.

4. 4

   Verify coolant hose routing to the DEF tank heater; incorrect routing (e.g., red band not connected to the top tube) can cause continuous hot water circulation, overheating the DEF tank and damaging the heater valve.

5. 5

   Check for related fault codes such as 3363-04 (short to ground), 3363-05 (open circuit), or 3363-31 (power stage over temp) to confirm a circuit integrity issue.

1. 1

   Preparation

   Turn off the machine, ensure the engine and coolant are cool, and disconnect the battery.

2. 2

   Locate the Valve

   Locate the DEF tank heater coolant valve, which is usually mounted near the engine block or inline with the coolant hoses running to the DEF tank.

3. 3

   Disconnect Electricals

   Unplug the electrical connector to the DEF tank heater valve.

4. 4

   Isolate the Coolant

   Partially drain the engine coolant or use hose pinch-off pliers on the coolant lines leading to and from the valve to prevent excessive fluid loss.

5. 5

   Remove the Valve

   Loosen the hose clamps, disconnect the coolant hoses from the valve, remove the mounting hardware, and extract the faulty valve.

6. 6

   Install the New Valve

   Mount the replacement DEF tank heater coolant valve. Reconnect the coolant hoses, ensuring they are routed to the correct ports (e.g., red band to the top tube).

7. 7

   Reconnect and Refill

   Reconnect the electrical connector. Remove the hose pinch-off pliers (or refill the engine coolant) and bleed the cooling system of any air.

8. 8

   Clear Codes and Test

   Reconnect the battery. Use an Electronic Service Tool (EST) to clear the fault codes. Run the engine and perform a fault verification test to ensure the code does not return and the valve cycles properly.