Case IH 19183 – DCU (Dosing Control Unit) / ATC (Aftertreatment Control): Reverting valve (4-2way valve?) electrically | Open load | P20A0 Vent valve (Reductant Purge Control Valve) -open circuit

This code indicates an electrical 'open load' (open circuit) in the circuit controlling the reverting valve (also referred to as the reductant purge control valve or vent valve). An open circuit means the control module cannot detect electrical continuity through the valve's solenoid or its wiring.

• Tier 4a
• Magnum 235
• Magnum 260
• Magnum 290
• Magnum 315
• Magnum 340 (Series 4)
• Steiger 350 through 600
• Puma 145
• Puma 210
• Axial-Flow Combine 7230
• Axial-Flow Combine 8230
• Axial-Flow Combine 9230
• Axial-Flow Combine 7240

1. 1

   Visually inspect the wiring harness and connectors between the DCU and the DEF Supply Module for physical damage, chafing, or disconnected plugs.

2. 2

   Disconnect the DCU harness connector and the DEF supply module connector. Inspect for water intrusion, corrosion, or pushed-out pins on the reverting valve power and ground circuits.

3. 3

   Measure the resistance of the reverting valve circuit from the DCU connector to the valve connector. An infinite resistance (OL) indicates a broken wire.

4. 4

   Measure the resistance across the reverting valve solenoid pins directly at the DEF supply module. If the solenoid shows an open circuit internally, the valve/module has failed.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Repair Wiring

   If the diagnostic checks revealed a broken wire or corroded connector in the harness between the DCU and the DEF supply module, repair the wiring fault or replace the damaged connector pigtail.

3. 3

   Replace the Valve/Module

   If the wiring is intact but the valve itself is open internally, the reverting valve must be replaced. Relieve any residual pressure in the DEF lines. Disconnect the electrical harness, DEF inlet/outlet lines, and coolant lines from the DEF supply module. Unbolt and remove the faulty module. Install the new DEF supply module and reconnect all lines and harnesses.

4. 4

   System Bleed and Test

   Reconnect the battery. Use the Case IH EST (Electronic Service Tool) to clear the fault codes. Run a DEF system commissioning test or dosing test to prime the system, check for leaks, and verify that the reverting valve operates correctly during the purge cycle.