New Holland DCU 19344 – DCU: Coolant control valve mechanically defective blocked closed / Vent valve (Reductant Purge Control Valve) - open circuit.

The system has detected a mechanical blockage or failure in the DEF/AdBlue coolant control valve (which regulates engine coolant flow to heat the DEF tank and prevent freezing). Simultaneously, it flags an open electrical circuit in the reductant purge control valve (vent valve), meaning the electrical connection to the valve is broken, unplugged, or the internal solenoid has failed.

• T6 series
• T7 series
• T8 series
• CR series
• CR9090
• CX Elevation series
• W-series
• W130D
• W170D
• W190C
• W230C
• LM series
• LM7.35

1. 1

   Inspect the wiring harness leading to the SCR coolant control valve and the reductant purge control valve for chafed wires, disconnected plugs, or corroded pins (addresses the open circuit cause).

2. 2

   Remove the coolant control valve and perform a pressure/flow test by blowing through the inlet while holding the bottom port closed to see if it seals correctly (addresses the mechanical blockage cause).

3. 3

   Ensure the coolant lines are installed and routed correctly, as incorrect routing can cause DEF to overheat or fail to thaw.

4. 4

   Inspect the DEF supply lines, pump motor hoses, and O-rings for air leaks or blockages.

1. 1

   Preparation

   Turn off the machine, disconnect the battery, and allow the engine and exhaust system (DOC/SCR) to cool completely.

2. 2

   Locate the Valve

   Locate the SCR coolant control valve and supply module. On many wheel loaders and tractors, this is attached to the support structure of the DOC.

3. 3

   Disconnect Electricals

   Disconnect the electrical connector from the SCR coolant control valve and the reductant purge control valve.

4. 4

   Isolate Coolant

   Clamp off the engine coolant hoses leading to the valve to prevent excessive coolant loss.

5. 5

   Remove Lines

   Disconnect the coolant line connectors from the SCR coolant control valve.

6. 6

   Dismount the Valve

   Remove the retaining brackets or bolts securing the valve to the support structure.

7. 7

   Install the New Part

   Mount the replacement coolant control/purge valve, reconnect the coolant lines, and securely plug in the electrical harness.

8. 8

   Reassemble and Clear

   Unclamp the coolant lines, top off the engine coolant if any was lost, and reconnect the battery. Use a diagnostic scan tool to clear the DCU 19344 / P20A0 fault codes and run a DEF system commissioning/dosing test to verify the repair.