Case IH 19264 (F-3363-05) - ECU – DCU (Dosing Control Unit): DEF/AdBlue tank heater actuator open load failure

The control module has detected an open circuit (infinite resistance) in the electrical circuit for the DEF tank heater coolant control valve solenoid. This valve regulates the flow of hot engine coolant through the DEF tank heating coil to prevent the diesel exhaust fluid from freezing in cold weather.

• VESTRUM CVX
• Case IH Magnum Series (235–340 Series 4)
• Case IH Steiger Series (350–600 HP)
• Case IH 240 Series Axial-Flow Combines
• Case IH Puma
• Case IH Maxxum
• Case IH Farmall

1. 1

   Visual & Harness Inspection: Inspect the wiring harness between the DCU and the DEF tank heater coolant control valve (CCV). Look for broken wires, chafing, or disconnected plugs.

2. 2

   Solenoid Resistance Test: Disconnect the electrical connector at the DEF tank heater valve and measure the resistance across the valve's solenoid pins using a multimeter. If the reading shows an open circuit (infinite resistance/OL), the internal coil of the valve is broken, and the valve must be replaced.

3. 3

   Relay & Fuse Check: Check the DEF supply module heater relays and fuses in the power distribution box, as a blown fuse or failed relay can sometimes mimic an open circuit on the supply side.

4. 4

   Hose Routing Verification: Verify that the DEF tank coolant hoses are installed correctly. The DEF heater line with the 'red' band must be connected to the top tube running to the front part of the engine head.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the Valve

   Locate the DEF/AdBlue Coolant Control Valve (CCV). It is typically mounted inline with the coolant hoses routing from the engine block to the DEF tank.

3. 3

   Isolate Coolant

   Clamp off the engine coolant supply and return lines on both sides of the heater valve to prevent excessive coolant loss.

4. 4

   Removal

   Disconnect the electrical connector from the valve. Loosen the hose clamps and pull the coolant hoses off the valve fittings. Remove the mounting bolts securing the valve bracket to the chassis or engine block.

5. 5

   Installation

   Mount the new DEF tank heater control valve and secure the retaining bolts (torque to spec, e.g., 73-80 lb-ft depending on the exact bracket). Reconnect the coolant hoses, ensuring the correct routing (red band to the top tube if applicable). Tighten the hose clamps.

6. 6

   Reconnect

   Plug in the electrical connector. Remove the hose clamps.

7. 7

   Refill & Bleed

   Reconnect the battery. Top off the engine coolant reservoir if any fluid was lost. Start the engine and let it reach operating temperature to bleed any air from the cooling system.

8. 8

   Clear & Test

   Use a diagnostic scan tool (like the Case IH EST or Jaltest) to clear the 19264 / P20B1 fault code. Run a 'DEF Tank Heater Test' or 'Dosing Unit Override Test' via the software to command the valve ON and verify the open load fault does not return.