New Holland DCU 19289 – DCU: Downstream Catalyst Temperature Too Low

This code indicates that the engine control system has detected that the exhaust temperature downstream of the Selective Catalytic Reduction (SCR) catalyst is not reaching the expected operating temperature within the designated time frame. It points to a range or performance issue with the downstream catalyst temperature sensor circuit, meaning the sensor is either failing to read correctly, there is an electrical fault in its circuit, or the exhaust system is physically failing to heat up due to an exhaust leak.

• T6
• T7
• T8
• TS6.110
• TS6.120
• W190B
• W50BTC
• L334
• C362
• Magnum 235-340
• 721F-921F

1. 1

   Inspect the exhaust system and SCR muffler for any physical damage, exhaust leaks, or loose clamps before the downstream sensor.

2. 2

   Inspect the wiring harness leading to the downstream catalyst temperature sensor for chafed wires, melted insulation, or corrosion inside the connector.

3. 3

   Using a diagnostic scan tool, monitor the live data for the downstream catalyst temperature sensor and compare it to the upstream sensor and ambient temperature when the engine is cold.

4. 4

   Check for open circuits or short-to-ground conditions on the sensor signal wire leading back to the DCU.

1. 1

   Cool down exhaust

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

2. 2

   Locate the sensor

   Locate the downstream catalyst temperature sensor mounted at the exhaust outlet pipe, directly after the SCR muffler/catalytic converter.

3. 3

   Clear access

   Remove the SCR muffler's upper heat shield if necessary to access the sensor.

4. 4

   Disconnect sensor

   Carefully unplug the electrical connector for the temperature sensor.

5. 5

   Remove sensor

   Use an appropriate sensor socket or wrench to unscrew the sensor from the exhaust pipe. If seized, apply penetrating oil and allow it to sit before attempting removal to avoid stripping threads.

6. 6

   Install new sensor

   Apply a small amount of anti-seize compound to the threads of the new sensor. Thread the new sensor into the exhaust pipe by hand to prevent cross-threading, then tighten to the OEM torque specification.

7. 7

   Reassemble

   Reconnect the electrical connector and reinstall any heat shields or clamps that were removed.

8. 8

   Clear codes and test

   Use a diagnostic tool to clear the DCU 19289 / P042B fault codes and run the machine through a stationary regeneration or warm-up cycle to verify the repair.