New Holland DCU 19074 – DCU: Voltage supply 2 -tube heaters (UB2) electrical | Open circuit to UB2 | P20C1 Reagent -suction tube heating -open circuit

The system has detected an open electrical circuit on Voltage Supply 2 (UB2), which is responsible for powering the DEF (Diesel Exhaust Fluid / Reagent) suction tube heater. An open circuit indicates a broken wire, a disconnected plug, a burned-out heater element in the suction line, or an internal failure within the pump module's power stage.

• T6 Series
• T7 Series
• T8 Series
• T9 Series
• CR Series
• CX Series
• CR9090
• CX8080
• CX8090

1. 1

   Visually inspect the wiring harness and connectors between the DCU, the DEF pump module, and the DEF suction tube heater for disconnected plugs, chafed wires, or corroded pins.

2. 2

   Use a multimeter to verify continuity on the UB2 circuit between the DCU and the suction tube heater to rule out a broken wire in the external harness.

3. 3

   Measure the resistance of the DEF suction tube heater element. An open reading (infinite ohms) indicates the heater element itself has failed.

4. 4

   If the external wiring and tube heater test good, verify the pump module for an internal failure on the UB2 circuit.

1. 1

   Turn off ignition and disconnect battery

   Turn off the ignition (Key 15 off) and disconnect the battery ground to ensure electrical safety.

2. 2

   Locate DEF components

   Locate the DEF pump module and the DEF tank suction line on the machine.

3. 3

   Disconnect electrical harness

   Disconnect the electrical harness at the DEF suction tube heater and the pump module.

4. 4

   Perform electrical checks

   Perform the continuity and resistance checks outlined above.

5. 5

   Repair or replace external harness

   If a broken wire is found in the external harness, repair the wire or replace the affected harness section.

6. 6

   Replace DEF suction line assembly

   If the suction tube heater element tests open, replace the DEF suction line assembly.

7. 7

   Disconnect pump module lines and connectors

   If the external wiring and tube heater test good, the fault lies internally within the DEF pump module. Disconnect the DEF fluid lines and electrical connectors from the pump module.

8. 8

   Remove faulty DEF pump module

   Unbolt and remove the faulty DEF pump module.

9. 9

   Install new DEF pump module

   Install the new DEF pump module and reconnect all fluid lines and electrical plugs.

10. 10

    Clear fault code

    Reconnect the battery, turn the ignition on, and use a diagnostic tool (such as New Holland EST) to clear the DCU 19074 / P20C1 fault code.

11. 11

    Run machine to verify repair

    Run the machine to ensure the DEF system primes successfully and the code does not return.