New Holland DCU 19775 – DCU (Dosing Control Unit): Group error path catalyst temperature — Error belonging to group catalyst temperature out of range — P0426 Plausibility of catalyst temperature sensors - Plausibility error (static)

The system has detected an implausible reading from the exhaust gas temperature (EGT) sensors located in the catalyst/SCR (Selective Catalytic Reduction) system. The temperatures reported by the upstream and downstream sensors do not make logical sense when compared to each other or to the expected operating conditions.

• New Holland T7 series
• New Holland T8 series (e.g., T8.xxx)
• New Holland W-Series Wheel Loaders (e.g., W50C, W80C, W100D)

1. 1

   Inspect the exhaust gas temperature sensors (located before and after the DOC/SCR catalyst) and their wiring harnesses for physical damage, melting, or corrosion.

2. 2

   Disconnect the sensor and check the 2-pin connector for water intrusion or bent pins. Test the harness for continuity, open circuits, or shorts to ground.

3. 3

   Use a multimeter to measure the resistance of the EGT sensors. Compare the upstream and downstream sensors; a completely open circuit or a drastically different resistance value at ambient temperature indicates a failed sensor.

4. 4

   Inspect the exhaust piping before the catalyst for leaks. An exhaust leak can cause skewed temperature readings, triggering a plausibility error.

1. 1

   Safety First

   Turn off the machine, allow the exhaust system to cool completely, and disconnect the battery.

2. 2

   Locate the Faulty Sensor

   Identify which sensor is failing (upstream or downstream of the SCR/DOC) based on your multimeter tests or live data from a diagnostic scan tool.

3. 3

   Remove the Sensor

   Disconnect the sensor's electrical connector. Use a specialized EGT sensor socket or a flare nut wrench to carefully unscrew the sensor from the exhaust pipe (typically an M14x1.5 thread).

4. 4

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Thread it in by hand to prevent cross-threading, then tighten to OEM torque specifications.

5. 5

   Reconnect

   Plug the 2-pin electrical connector back into the machine's harness.

6. 6

   Clear Codes and Test

   Reconnect the battery. Use a diagnostic tool to clear the DCU 19775 / P0426 fault codes. Start the engine and perform a stationary forced regeneration or a test drive to ensure the sensors read plausibly and the code does not return.