New Holland DCU 19183 – DCU: Reverting valve (4-2way valve?) electrically | Open load | P20A0 Vent valve (Reductant Purge Control Valve) - open circuit

The control module has detected an 'open load' (an open electrical circuit or lack of continuity) in the circuit for the DEF (Diesel Exhaust Fluid) reverting valve. An open circuit means the valve cannot be actuated, which will prevent the system from purging and will likely trigger an engine derate or inducement.

• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T8.275
• T8.300
• T8.330
• T8.360
• T8.390
• W190B

1. 1

   Verify the Fault: Check if the fault is currently active. If it is intermittent, it is highly likely to be a wiring or connector issue.

2. 2

   Visual Inspection: Inspect the main electrical connector at the DEF Supply Module (pump) for water intrusion, corrosion, or adhering foreign material.

3. 3

   Harness Continuity Test: Disconnect the harness from the DCU and the DEF pump. Check for continuity on the reverting valve power supply and ground circuits (e.g., ECU Connector-1 pin 85 to the supply module).

4. 4

   Check for Shorts/Opens: Ensure there is no short to ground, short to battery, or high resistance in the wiring harness between the DCU and the DEF pump.

5. 5

   Component Resistance Test: Measure the resistance across the reverting valve pins directly on the DEF pump. If the multimeter reads an open circuit (infinite resistance), the internal solenoid coil of the reverting valve has failed.

1. 1

   Depressurize and Drain

   Ensure the ignition is off and the system has completed any delayed after-run cycles. Disconnect the battery.

2. 2

   Disconnect Lines

   Carefully disconnect the DEF supply, return, and dosing fluid lines from the DEF Supply Module. Be prepared to catch any residual DEF fluid.

3. 3

   Remove the DEF Pump

   Disconnect the electrical harness and unbolt the DEF Supply Module from its mounting bracket. Note: OEM procedures dictate replacing the entire DEF Supply Module assembly when the internal reverting valve fails electrically.

4. 4

   Install the New Pump

   Mount the replacement DEF Supply Module, reconnect the fluid lines, and plug in the electrical connector.

5. 5

   Software Reset

   Reconnect the battery. Use the New Holland Electronic Service Tool (EST) or equivalent PT-Box tool to perform an 'Inducement Unlock' or 'Counter Reset' to clear the SCR lockouts.

6. 6

   System Test

   Run the engine and use the diagnostic tool to command a pressure build-up and subsequent purge cycle to verify the new reverting valve operates correctly without logging DCU 19183.