New Holland DCU 19064 – DCU (Dosing Control Unit): Voltage supply internal heaters 1 (UB1) electrical | Open circuit to UB1 | P20C5 Pump module - Internal heating - open circuit.

The engine's emissions system has detected an open electrical circuit in the internal heating element of the Diesel Exhaust Fluid (DEF) pump module. The internal heater is critical for thawing frozen DEF (AdBlue) in cold climates and preventing the fluid from freezing during operation. Because the circuit is "open," the electrical current cannot complete its path, meaning the heater is completely inoperative.

• T4
• T5
• T6
• T6.120
• T6.140
• T6.175
• T7
• T7.170
• T7.210
• T7.260
• T8
• T8.320
• T8.355
• T9
• TS6 series
• CR series
• CR6090
• CR8.90
• CR9090
• CX series
• CX8070
• CX8090
• 9000 series harvesters
• LM series
• LM6.32
• LM7.42
• LM9.35
• TH series
• Speedrower 160
• Speedrower 220
• Speedrower 260
• WD series
• Stackcruiser models

1. 1

   Inspect the wiring harness between the Dosing Control Unit (DCU) and the DEF pump module for chafed wires, broken connections, or corrosion that could cause an open circuit.

2. 2

   Disconnect the DEF pump module and check the connector pins for pushed-out terminals, moisture, or DEF crystal buildup.

3. 3

   Verify the DEF heater relays and fuses (specifically the switched power relays supplying the DCU and pump module) to ensure power is being sent to the heater circuit.

4. 4

   Test the internal resistance of the DEF pump's heater coil using a multimeter. If it reads 'OL' (Open Loop) or infinite resistance, the internal heater has failed.

1. 1

   Depressurize and Drain

   Ensure the machine is turned off and the DEF system has completed its purge cycle (do not disconnect the battery immediately after key-off). Drain the DEF fluid from the supply lines if necessary.

2. 2

   Remove the DEF Pump Module

   Disconnect the electrical connectors and the DEF suction, pressure, and backflow lines from the DEF pump (Denoxtronic Supply Module). Unbolt the module from its mounting bracket.

3. 3

   Install the Replacement Module

   Mount the new DEF pump module and reconnect the fluid lines, ensuring they click securely into place to prevent leaks. Reconnect the electrical harness.

4. 4

   Software Calibration

   A new DEF pump module will likely need to be programmed/calibrated to the vehicle's DCU using the OEM diagnostic software (e.g., CNH Electronic Service Tool) to clear the fault codes and initialize the pump.

5. 5

   System Prime and Test

   Turn the key on and use the diagnostic tool to run a DEF pump prime test and a heater diagnostic test to verify the open circuit is resolved and the system builds pressure.