New Holland DCU 19084 – DCU (Dosing Control Unit): Voltage supply 3 - Coolant control valve and reverting valve (UB3) electrical | Short circuit to Ground UB3 | P20A2 Vent valve (Reductant Purge Control Valve) - short circuit low

The Dosing Control Unit has detected a short circuit to ground on the "UB3" voltage supply circuit. This specific circuit provides power to the DEF (Diesel Exhaust Fluid) system's coolant control valve and the reverting/vent valve (also known as the reductant purge control valve). Because the circuit is shorted to ground, the voltage is pulled low, preventing these valves from operating correctly.

• T6 series
• T7 series
• T8 series
• T9 series
• TS6 series
• T7.210
• T8.320
• TS6.120
• CR series
• CX series
• CR9090
• CX8080
• 9090X
• LM series
• TH series
• LM7.35
• TH7.42
• Speedrower series
• SP series sprayers

1. 1

   Visually inspect the wiring harness running from the DCU to the coolant control valve and the reductant purge control valve for chafed wires, melted insulation, or pinch points shorting to the chassis.

2. 2

   Disconnect the electrical connectors at the reductant purge control valve and the coolant control valve to see if the active fault code changes to an open circuit (19083 / P20A0), indicating an internal valve short.

3. 3

   Check for related codes (such as 15651) that indicate an internal electrical failure of the DCU pump module on the UB3 circuit.

1. 1

   Turn off the machine and disconnect the battery to ensure safety while working on the electrical system.

2. 2

   Locate the DEF pump module (DCU), the coolant control valve, and the reductant purge control valve.

3. 3

   If the diagnostic checks revealed a damaged wiring harness, repair the shorted section of the wire using OEM-approved splicing methods and heat-shrink tubing, or replace the affected harness section.

4. 4

   If the diagnostic checks isolated the short to one of the valves, remove the faulty valve (either the coolant control valve or the reductant purge control valve) and install a replacement.

   If replacing the coolant control valve, you may need to clamp the coolant lines to prevent fluid loss.

5. 5

   If the wiring and valves are completely intact but the UB3 circuit is still grounded at the module pins, the DCU (DEF pump module) has failed internally. Remove the DEF pump module and install a new one.

6. 6

   Reconnect the battery.

7. 7

   Connect an Electronic Service Tool (EST) to the machine, clear the inactive fault codes, and run a DEF system test/purge cycle to verify the repair.

   If the DCU was replaced, the new module will need to be programmed/calibrated to the vehicle using the EST.