Case IH 19069 (DTC 181A) - ECU – Engine Control Unit (ECU): Upstream SCR catalyst temperature too high

The exhaust gas temperature entering the Selective Catalytic Reduction (SCR) chamber has exceeded the maximum allowable threshold. This condition can trigger an engine inducement (power derate), which may automatically reduce the engine to low idle speed after 30 seconds to protect the aftertreatment system.

• MAXXUM T4E
• 240 Series Axial-Flow® Combines
• N Series Loaders / Loader Backhoes (e.g., 580N)

1. 1

   Check for related active faults, specifically DTC 362C (SPN 13868) or DTC 291A (SPN 10522). If these are active, diagnose and resolve them first.

2. 2

   Verify if the fault is currently active using the CNH Electronic Service Tool (EST) or PT-Box.

3. 3

   Physically inspect the upstream SCR temperature sensor for proper installation, ensuring it is not incorrectly mounted, loose, or physically damaged.

4. 4

   Inspect the wiring harness for the upstream SCR temperature sensor (Pin 1: 5-volt supply, Pin 2: Common ground to the ECU) for short circuits, open loads, or damaged pins.

5. 5

   Ensure the DEF dosing system is functioning correctly, as improper dosing or a stuck exhaust flap can cause abnormal exhaust temperatures.

1. 1

   Resolve Circuit Issues

   If the diagnostic checks reveal damaged wiring or a loose connection at the sensor harness, repair the wiring or secure the connection.

2. 2

   Replace the Sensor

   If the wiring is intact but the sensor is faulty or reading out of range (causing the false 'too high' reading), remove the faulty upstream SCR temperature sensor from the catalytic chamber and install a new one.

3. 3

   Perform Inducement Unlock

   Because this fault causes an engine inducement (power loss/idle lock), you must perform an Inducement Unlock / Counter Reset using the CNH EST diagnostic tool once the physical repair is resolved.

4. 4

   Clear Codes and Test

   Clear the inactive fault codes from the ECU. Run the engine under load to verify that the upstream SCR temperature reads within the normal operating range (typically 480°F - 1020°F / 250°C - 550°C for optimal SCR efficiency) and that the code does not return.