New Holland DCU 19163 – DCU: Cooling control valve short circuit to UBat or open load | short circuit to battery | P20A3 Vent valve (Reductant Purge Control Valve) - short circuit high

The system has detected that the electrical circuit controlling the Reductant Purge Control Valve (also referred to as the DEF vent valve or cooling control valve) has a short to battery voltage (UBat). This prevents the valve from operating correctly, which can disrupt the DEF (Diesel Exhaust Fluid) purging or thawing process.

• T6
• T7
• T8
• T9
• Magnum
• Steiger

1. 1

   Connect the New Holland Electronic Service Tool (EST) to confirm DCU 19163 / P20A3 is active.

2. 2

   Inspect the wiring harness leading to the Reductant Purge Control Valve for chafing, melted insulation, or pinched wires that could introduce battery voltage.

3. 3

   Disconnect the valve's electrical connector and check for water ingress, corrosion, or bent pins.

4. 4

   Use a multimeter to test the harness side of the connector for a short to battery voltage with the key on. If the harness tests fine, the short circuit is likely internal to the valve's solenoid.

1. 1

   Depower the System

   Turn off the ignition and disconnect the tractor's battery to prevent electrical spikes or accidental DEF dosing.

2. 2

   Locate the Valve

   Locate the DEF supply module/pump assembly to access the Reductant Purge Control Valve.

3. 3

   Repair Wiring (If Applicable)

   If your multimeter tests indicated a harness short, trace the wire back toward the DCU, locate the damaged section, and splice in a weather-sealed repair.

4. 4

   Replace the Valve (If Applicable)

   If the valve itself is internally shorted: Clean the area around the valve to prevent dirt from entering the DEF system. Disconnect the electrical connector and carefully remove the DEF/coolant lines attached to the valve (have a catch pan ready for minor fluid loss). Unbolt and remove the faulty valve. Install the new valve, torque the mounting hardware to spec, and reconnect the fluid lines securely.

5. 5

   Reassembly and Testing

   Reconnect the electrical connector and the battery.

6. 6

   Clear and Verify

   Use the EST to clear the DCU 19163 fault code. Run a manual DEF system purge/dosing test via the software to ensure the valve operates correctly and the code does not return.