New Holland DCU 19164 – DCU: Cooling control valve short circuit to UBat or open load | Open load | Vent valve (Reductant Purge Control Valve) - open circuit

This fault code indicates a critical electrical issue within the Diesel Exhaust Fluid (DEF) / Selective Catalytic Reduction (SCR) system. Specifically, the system has detected an open circuit or a short to battery voltage (UBat) in the circuit for the Reductant Purge Control Valve (also referred to as the cooling control valve or vent valve). This valve is responsible for purging DEF from the lines back into the tank when the machine is shut down to prevent the fluid from freezing and expanding.

• T6
• T7
• T8
• CR9090
• CX8080

1. 1

   Connect a diagnostic scan tool to verify if DCU 19164 (P20A0) is active and check for related codes like P20A2 or P20A3.

2. 2

   Inspect the wiring harness and connectors between the DCU and the DEF supply module/purge control valve for chafed wires, corrosion, or disconnected pins.

3. 3

   Use a multimeter to test the wiring for continuity to ensure there is no open load or short to battery voltage (UBat).

4. 4

   Measure the resistance of the Reductant Purge Control Valve solenoid itself; an infinite resistance reading confirms an internal open circuit.

5. 5

   Check for cascading codes, such as ECM DTC P20C9, which may require clearing after the primary repair.

1. 1

   Power Down

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

2. 2

   Access the DEF Supply Module

   Locate the Urea Fluid Supply Module (DEF pump assembly), which houses the Reductant Purge Control Valve.

3. 3

   Harness Repair (If Applicable)

   If the diagnostic checks revealed a broken wire or short to battery voltage in the harness, repair the damaged section of the wiring and replace any corroded connector pins.

4. 4

   Valve / Module Replacement

   If the wiring is intact but the valve solenoid has failed (open circuit), replace the Reductant Purge Control Valve. Note: On many CNH applications, this valve is integrated into the Urea Fluid Supply Module. If it cannot be serviced separately, remove and replace the entire DEF Supply Module assembly.

5. 5

   Reassembly

   Reconnect all electrical connections and the battery.

6. 6

   Clear Codes

   Use the diagnostic scan tool to clear the DCU 19164 (P20A0) fault code, as well as any secondary codes like P20C9.

7. 7

   System Test

   Cycle the key, run the engine, and perform a system test to ensure the DEF pump and purge valve operate correctly and the fault code does not return.