New Holland DCU 19379 – DCU: UREA Temperature too low during commissioning | Temperatures not plausible during commissioning.

This fault indicates that during the startup (commissioning) phase of the emissions system, the temperature reading of the Diesel Exhaust Fluid (DEF / Urea) is either implausibly low or does not align with expected environmental parameters (such as ambient air or engine coolant temperatures).

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1. 1

   Verify that the DEF tank has adequate, uncontaminated fluid and is not frozen solid due to a failed tank heater.

2. 2

   Inspect the wiring harness connecting the DCU to the DEF pump module and the DEF tank header for chafed wires, corrosion, or loose pins.

3. 3

   Using the New Holland Electronic Service Tool (EST), monitor the live DEF temperature reading and compare it against ambient air and engine coolant temperatures after a cold soak.

4. 4

   Determine whether the implausible reading originates from the temperature sensor inside the DEF pump module or the sensor in the DEF tank header/sending unit.

1. 1

   Connect the New Holland EST diagnostic tool to read and clear the active DCU 19379 code.

   Cycle the key to see if the code immediately returns during the system's commissioning phase.

2. 2

   Perform a visual and multimeter inspection of the DEF temperature sensor circuit.

   Disconnect the sensor harness at the DEF pump or tank header and test for proper reference voltage and ground supplied by the DCU.

3. 3

   Test the continuity of the signal wire from the sensor connector back to the DCU harness pin.

4. 4

   Evaluate the temperature sensor.

   If the wiring harness is intact and providing the correct voltage, but the EST still shows an implausible temperature reading, the temperature sensor itself has failed.

5. 5

   Replace the faulty component.

   Because the DEF temperature sensor is often integrated into larger assemblies, replace either the DEF Pump Module or the DEF Tank Header Unit, depending on which sensor is flagging the implausible data on your specific model.

6. 6

   Reconnect all harnesses, turn the ignition on, and allow the DCU to perform its commissioning sequence.

7. 7

   Clear the fault codes and run the machine.

   Verify the SCR system enters closed-loop dosing without triggering an engine derate.