Case IH 19187 (F-3224-16) - ECU – Engine ECU: Upstream NOx sensor self-diagnosis result is higher than the limit.

The upstream Nitrogen Oxide (NOx) sensor—located in the exhaust stream before the Diesel Oxidation Catalyst (DOC) and Selective Catalytic Reduction (SCR) unit—is reporting self-diagnostic values that exceed the maximum allowable threshold. The FMI 16 identifier specifically means the data is valid but above the normal operating range (moderately severe level) or is registering as invalid data.

• VESTRUM CVX
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Steiger (535, 540, 580, 620)
• Magnum
• Puma
• Optum

1. 1

   Verify the physical presence and correct connection of the upstream NOx sensor to the CAN network.

2. 2

   Inspect the wiring harness and connectors (specifically connector C186 / X186) for corrosion, backed-out pins, or damage.

3. 3

   Check the correct functioning of the CAN controller to ensure the sensor is communicating properly with the Engine ECU.

4. 4

   Verify that the NOx sensor supply voltage is within the correct operating range, as voltage spikes or drops can trigger false sensor limits.

5. 5

   Ensure there are no aftermarket engine tuning chips installed, as these are known to interfere with the NOx sensor signal.

1. 1

   Cool down exhaust

   Ensure the engine is turned off and the exhaust system has completely cooled, as the sensor is located on the hot side of the exhaust before the DOC.

2. 2

   Disconnect sensor

   Locate the upstream NOx sensor and carefully disconnect its 5-cavity electrical connector from the engine wiring harness.

3. 3

   Remove faulty sensor

   Use a specialized NOx/O2 sensor socket or wrench to unthread the faulty sensor from the exhaust pipe.

4. 4

   Install new sensor

   Thread the new upstream NOx sensor into the exhaust pipe and tighten it to the manufacturer's specified torque.

5. 5

   Reconnect harness

   Plug the sensor's electrical connector back into the harness, ensuring the weather seal and locking tab engage properly.

6. 6

   Verify and warm-up

   Clear the fault codes using a diagnostic tool. Turn the key switch ON and start the engine. Monitor the sensor data; the sensor will initially read 'not ready' until the exhaust heat wicks moisture off the tip of the sensor (reaching its 'Dew Point'). Once it switches to 'Ready,' verify that the fault code does not return.