Case IH 19187 – Engine Control Unit (ECU): Upstream NOx sensor self-diagnosis result is higher than the limit.

The upstream NOx sensor's internal self-diagnostic check yielded a value that exceeds the programmed maximum threshold, indicating that either the sensor itself is internally failing/out of calibration, or the engine is producing an extreme, out-of-range level of NOx emissions.

• Tier 4b
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Steiger Series Tractors (Steiger 580 Tier 4B)
• Magnum Series Tractors (235, 340)

1. 1

   Inspect the upstream NOx sensor wiring harness and connector (Connector C186) for chafing, melted wires, or loose/corroded terminals.

2. 2

   Inspect the exhaust manifold and piping prior to the DOC for any exhaust leaks. Leaks can introduce excess oxygen or alter pressure, skewing the NOx sensor readings.

3. 3

   Check for concurrent engine codes related to fuel injection timing, boost pressure, or intake manifold temperatures. Over-advanced fuel injection timing or over-boost conditions can cause actual engine-out NOx to spike beyond the sensor's readable limit.

4. 4

   Use the Case IH Electronic Service Tool (EST) to monitor the upstream NOx sensor voltage and ppm readings. If the sensor voltage is stuck high or erratic, the sensor is likely internally shorted or degraded.

1. 1

   Preparation

   Park the machine on a level surface, turn off the engine, and allow the exhaust system to cool completely to avoid severe burns.

2. 2

   Disconnect Power

   Disconnect the machine's battery to prevent electrical shorts and reset the module's baseline memory.

3. 3

   Locate the Sensor

   Locate the upstream NOx sensor. It is threaded into the exhaust pipe directly after the turbocharger and before the DOC/SCR catalyst assembly.

4. 4

   Disconnect Wiring

   Unclip the 5-cavity electrical connector (C186) connecting the NOx sensor to the engine wiring harness.

5. 5

   Remove the Sensor

   Using a specialized NOx/O2 sensor socket (usually 22mm or 24mm depending on the engine), carefully unthread the sensor from the exhaust pipe.

6. 6

   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-coated). Thread it in by hand to prevent cross-threading, then tighten to the OEM torque specification.

7. 7

   Reconnect

   Plug the new sensor's electrical connector back into the harness, ensuring the locking tab clicks into place. Reconnect the battery.

8. 8

   Clear Codes and Test

   Connect the Case IH EST diagnostic laptop, clear the inactive 19187 / 11CE fault code, and perform an engine run-up or stationary regeneration to verify the sensor reads correctly and the code does not return.