Case IH 19185 – Engine Control Unit (ECU): Upstream NOx Sensor Value is not within the expected range

The Upstream NOx Sensor is reading values outside of the expected parameters. The sensor reports a value that does not align with the engine's current operating calculations, flagging the reading as implausible.

• Tier 4b
• Case IH Magnum series (e.g., Magnum 340)
• Case IH Puma series (e.g., Puma 185, 200, 220, 240)
• Case IH Steiger series (e.g., Steiger 580)
• Case N-Series Loaders / STM N Series
• Equipment utilizing the F5 / FPT Tier 4B engines

1. 1

   Check for accompanying DEF dosing system codes or DPF regeneration faults, which can skew emissions readings

2. 2

   Inspect the wiring and CAN Bus for proper communication (look for CAN timeout errors such as code 3533)

3. 3

   Inspect the upstream NOx sensor harness connector (Connector C186) for damaged terminals, corrosion, or loose wires

4. 4

   Check for exhaust leaks in the piping between the engine block and the DOC, which can introduce outside oxygen and skew readings

1. 1

   Cool Down

   Ensure the machine is turned off and the exhaust system has completely cooled.

2. 2

   Disconnect Power

   Turn off the battery disconnect switch to prevent electrical shorts.

3. 3

   Locate the Sensor

   Locate the upstream NOx sensor, which is mounted in the exhaust pipe just before the Diesel Oxidation Catalyst (DOC).

4. 4

   Clear Access

   Depending on the tractor model, disengage the clamps from the exhaust pipe to the turbo or the DOC to gain wrench clearance if necessary.

5. 5

   Disconnect Wiring

   Disconnect the electrical connector for the NOx sensor from the main engine harness.

6. 6

   Remove the Sensor

   Carefully unscrew and remove the upstream NOx sensor from the exhaust pipe.

7. 7

   Install New Sensor

   Thread the new NOx sensor into the exhaust pipe. Do not use excessive anti-seize on the probe tip, as it can foul the sensor. Tighten to OEM torque specifications.

8. 8

   Reconnect

   Reconnect the sensor's electrical connector to the harness. Re-secure any exhaust clamps that were loosened.

9. 9

   Clear Codes

   Restore battery power, use a diagnostic tool to clear the inactive 19185 fault code, and run the engine to operating temperature to ensure the code does not return.