Case IH 19164 – DCU (Dosing Control Unit): Cooling control valve short circuit to UBat or open load | Open load | P20A0 Vent valve (Reductant Purge Control Valve) - open circuit

The control module has detected an open circuit (lack of electrical continuity) in the circuit for the Coolant Control Valve (also known as the Reductant Purge Control Valve or Vent Valve), which regulates the flow of engine coolant to the Diesel Exhaust Fluid (DEF) tank heater.

• Tier 4a
• Magnum Series (235, 250, 280, 310, 340 Series 4)
• Steiger Series (350, 400, 450, 500, 550, 600)
• Puma Series
• CX Series Excavators (CX170E, CX220E, CX260E)
• Farmall Series (Tier 4B final models)

1. 1

   Visually inspect the Coolant Control Valve (near the DEF supply module or tank) and wiring harness for chafing, breaks, or rodent damage.

2. 2

   Disconnect the electrical plug at the valve and check for pushed-out pins, corrosion, or moisture inside the connector.

3. 3

   Use a multimeter to check the resistance across the pins of the Coolant Control Valve. If the reading shows infinite resistance (OL), the valve's internal solenoid is open.

4. 4

   Check the voltage supply (UB3 circuit) from the DCU to the valve harness to ensure power is reaching the connector when commanded.

5. 5

   Check the ground circuit for continuity back to the DCU.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts. Allow the engine coolant to cool down completely.

2. 2

   Isolate Coolant

   Drain the engine coolant below the level of the valve, or use hose pinch-off pliers on the coolant lines leading to and from the Coolant Control Valve to minimize fluid loss.

3. 3

   Removal

   Disconnect the electrical connector from the valve. Loosen the hose clamps and remove the coolant lines from the valve. Remove the retaining bolts (often M14 or M6 bolts depending on the bracket) securing the valve/support bracket to the machine.

4. 4

   Installation

   Mount the new Coolant Control Valve and torque the retaining bolts to OEM specifications (e.g., 73 - 80 lb-ft for heavy bracket bolts, if applicable). Reconnect the coolant hoses and secure the clamps. Reconnect the electrical connector.

5. 5

   Post-Repair

   Remove the hose pinch-off pliers or refill the engine coolant to the proper level. Reconnect the battery and turn the key on. Use an Electronic Service Tool (EST) or compatible scan tool to clear the DCU fault codes (19164 / P20A0). Run the machine and check for coolant leaks and ensure the code does not return.