Case IH 19775 – DCU (Dosing Control Unit): Group error path catalyst temperature – Plausibility of catalyst temperature sensors - Plausibility error (static).

The control module has detected that the temperature readings from the Selective Catalytic Reduction (SCR) catalyst temperature sensors are out of range, or the ratio/difference between the upstream (before catalyst) and downstream (after catalyst) temperature sensors is not plausible compared to the expected operating parameters.

• Tier 4b
• Magnum series (235–340 Series 4)
• Steiger series (350–600)
• Puma
• Optum
• Axial-Flow series (8230)
• F-Series Wheel Loaders (721F, 821F, 921F)
• 580N EP Backhoes
• T8.xxx Series
• T7 Series

1. 1

   Cold-Soak Test: Allow the engine to cool completely to ambient temperature. Use an Electronic Service Tool (EST) laptop to read the intake temperature sensor, the upstream SCR temperature sensor, and the downstream SCR temperature sensor. All three should read the exact same ambient temperature. If one sensor reads significantly higher or lower, that specific sensor is faulty.

2. 2

   Software Verification: Check if the DCU and Engine Control Module (ECM) have the latest software updates. Older software versions were highly prone to false plausibility codes and 'Exhaust Temperature Low' errors. Updating the software often resolves hyper-sensitive plausibility faults.

3. 3

   Physical Inspection: Inspect the exhaust gas piping and muffler for physical damage, exhaust leaks, or loose sensor mountings.

4. 4

   Wiring Check: Inspect the wiring harness connecting the SCR temperature sensors to the DCU for chafing, melted insulation, or moisture intrusion in the connectors.

1. 1

   Ensure safety and cool down

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

2. 2

   Disconnect sensor harness

   Locate the faulty SCR temperature sensor (either upstream or downstream of the DOC/SCR catalyst assembly) and disconnect its electrical harness.

3. 3

   Remove faulty sensor

   Carefully unscrew the faulty temperature sensor from the exhaust pipe/muffler bung.

4. 4

   Install new sensor

   Apply a high-temperature anti-seize compound to the threads of the new sensor (if not already pre-applied by the manufacturer). Thread the new sensor in and tighten to OEM torque specifications.

5. 5

   Reconnect harness

   Reconnect the electrical harness, ensuring the connector clicks into place and is routed away from direct heat sources.

6. 6

   Perform healing procedure

   The system must verify the repair to exit derate mode. Bring the engine up to operating temperature and run it under a heavy working load (achieving high exhaust temperatures, typically over 425°F) for up to 30 minutes. Once the SCR system registers plausible temperature ratios, it will 'heal' itself and clear the code. Alternatively, use an EST laptop to force a system reset.