New Holland DCU 19010 – DCU: Temperature sensor after catalyst (electrical) signal high P042D Catalyst Temperature Sensor Circuit High

The control module is receiving a voltage signal from the downstream Exhaust Gas Temperature Sensor (EGTS) that exceeds the maximum allowable threshold. This indicates an open circuit, a short to battery voltage in the wiring harness, or a completely failed sensor with infinite internal resistance.

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1. 1

   Scan Tool Verification: Connect a diagnostic tool (like the New Holland EST) to read live data from the DeNOx system. Compare the temperature reading of Sensor 1 (before catalyst) to Sensor 2 (after catalyst). If Sensor 2 is reading an impossibly high or maxed-out default value on a cold engine, the circuit is open.

2. 2

   Visual Inspection: Inspect the sensor, its connector, and the wiring harness routed along the exhaust. Look for melted wires, heat damage, chafing, or severe corrosion at the pins.

3. 3

   Circuit Testing: Disconnect the sensor and use a multimeter to measure the internal resistance of the sensor pins. If it reads 'OL' (open loop/infinite resistance), the sensor is dead and must be replaced.

4. 4

   Harness Testing: Backprobe the harness side of the connector with the ignition ON to ensure the DCU is sending the proper 5V reference signal and providing a good ground.

1. 1

   Cool Down

   Ensure the machine is turned off and the exhaust system has completely cooled to prevent severe burns.

2. 2

   Locate the Sensor

   Find the downstream exhaust gas temperature sensor. It is threaded into the exhaust pipe immediately after the SCR catalyst / DOC muffler assembly.

3. 3

   Disconnect Wiring

   Unplug the sensor's 2-pin electrical connector from the main engine harness.

4. 4

   Apply Penetrating Oil

   Spray the threads generously with penetrating oil and let it soak.

5. 5

   Remove the Sensor

   Using a line wrench or a specialized EGT sensor socket, carefully unscrew the sensor from the exhaust bung.

6. 6

   Clean the Threads

   Inspect the exhaust bung threads and clean them with a thread chaser if necessary to ensure the new sensor seats correctly.

7. 7

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize to the threads of the new sensor (avoid getting any on the probe tip). Thread it in by hand to prevent cross-threading, then tighten to OEM torque specifications.

8. 8

   Reconnect and Route

   Reconnect the electrical connector. Ensure the wiring is clipped back into its original retainers so it does not rest against the hot exhaust pipe.

9. 9

   Clear Codes

   Use your diagnostic tool to clear the DCU 19010 / P042D fault code. Run the engine through a warmup cycle to verify the live data reads correctly and the code does not return.