New Holland DCU 19307 – DCU (Dosing Control Unit): UREA pressure too high | Urea pressure not plausible (urea pressure too high) | P204B Reagent - pressure above threshold

The system's Diesel Exhaust Fluid (DEF / Urea) pressure sensor is detecting a pressure value that exceeds the maximum allowable operating threshold, or the pressure reading is implausible (e.g., the sensor reads high pressure even when the DEF pump is commanded off). This is typically caused by a blockage in the DEF delivery lines, a clogged dosing valve, a faulty pressure sensor, or a wiring short.

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1. 1

   Inspect the DEF pressure line and the DEF dosing valve (injector) for physical blockages or crystallized DEF fluid.

2. 2

   Unplug the DEF pump connector and the DCU connector, then measure resistance at the DCU connector across the sensor terminals to check for shorts to voltage or ground (should not be below 1.5 kilo-ohms).

3. 3

   Perform a sensor plausibility test using a diagnostic tool to monitor live DEF pressure with the key ON and engine OFF (reading high pressure when the pump is off indicates a failed sensor or circuit).

4. 4

   Check the DEF fluid quality to ensure it is not contaminated, which can accelerate crystallization and component failure.

1. 1

   Clean the System

   If a blockage is found in the DEF lines or the dosing valve, flush the lines with warm distilled water to dissolve the crystallized urea. Do not use harsh chemicals.

2. 2

   Repair Wiring

   If the harness test fails, locate the short or break in the wiring between the DCU and the DEF pump pressure sensor and repair/replace the harness.

3. 3

   Replace the DEF Pump/Sensor

   If the lines are clear and the wiring is intact, the internal pressure sensor inside the DEF supply module has likely failed. Replace the DEF pump assembly.

4. 4

   Replace the DEF Filter

   Whenever opening the DEF system or replacing the pump, always replace the main DEF supply filter.

5. 5

   Software Flash/Calibration

   If the entire DCU module is replaced, it will require a software flash and calibration using the New Holland Electronic Service Tool (EST) to clear the derate and resume normal operation.