New Holland DCU 19352 – DCU (Dosing Control Unit): Reverting valve (4-2way valve?) mechanically | valve does not open | P20A0 Vent valve (Reductant Purge Control Valve) - open circuit

The engine control unit has detected an open circuit in the reverting valve's electrical circuit, or the valve is mechanically stuck closed and failing to open during the purge cycle. This prevents the system from pumping DEF out of the lines and back into the tank when the machine is shut off.

• New Holland T7 Series Tractors
• New Holland T8 Series Tractors

1. 1

   Inspect the wiring harness and connectors between the DCU/ECU and the DEF Supply Module for damage, bent pins, pushed-out terminals, or corrosion.

2. 2

   Test the reverting valve circuits for an open load (check pins 11 and 12 on the ECU connector, or pins 8, 9, and 10 on the supply module side) and verify there is no short to ground or battery.

3. 3

   Connect a diagnostic scan tool, clear the DTC, and cycle the key. If P20A0 resets immediately but P20A2 does not, the issue is confirmed as an open circuit or internal module failure.

1. 1

   Power down system

   Turn off the ignition switch and wait for the aftertreatment system to completely power down (do not disconnect batteries immediately, as the system may be attempting a purge cycle).

2. 2

   Repair wiring or proceed to pump replacement

   If the wiring harness tested faulty during diagnostics, repair the broken wire or replace the damaged connector terminal. If the wiring is intact, proceed to replace the DEF pump.

3. 3

   Disconnect electrical connector

   Disconnect the electrical connector from the DEF Supply Module.

4. 4

   Disconnect fluid connectors

   Relieve any residual pressure and disconnect the fluid connectors (DEF suction, pressure, and return lines, as well as the 2 engine coolant lines used for heating the pump).

5. 5

   Remove faulty module

   Unbolt and remove the faulty DEF Supply Module from its mounting bracket.

6. 6

   Install new module

   Install the new DEF Supply Module and torque the mounting bolts to OEM specifications.

7. 7

   Reconnect lines

   Reconnect all DEF and coolant lines, ensuring they click into place securely.

8. 8

   Reconnect electrical harness

   Reconnect the electrical harness.

9. 9

   Clear codes and verify repair

   Turn the ignition ON, use a diagnostic scan tool to clear the DCU 19352 / P20A0 fault codes, and run an aftertreatment system test or reverting valve check to verify the repair.