Case IH 19555 – Engine Control Module (ECM) or Vehicle Control Module (VCM): Dynamic Monitoring of the NOx sensor

The engine's control system has detected an implausible signal or a lack of dynamic response from the Nitrogen Oxide (NOx) sensor.

• Tier 4b
• Case IH agricultural equipment
• Case Construction equipment (N-Series Tractor Loader Backhoes)

1. 1

   Scan All Modules: Use a diagnostic scan tool (such as the CNH EST) to read all fault codes. Determine if the fault is pointing to the upstream (engine-out) or downstream (post-SCR catalyst) NOx sensor.

2. 2

   Visual & Wiring Inspection: Inspect the sensor, its control module, and the wiring harness for visible damage, chafing, or melted wires. Check the electrical connector for water ingress, bent pins, or contact corrosion, which frequently cause communication drops.

3. 3

   Electrical Testing: Using a multimeter, verify the power supply, ground, and CAN bus communication lines at the sensor connector.

4. 4

   Check DEF/AdBlue Quality: Poor DEF quality can skew NOx readings and trigger dynamic monitoring faults. Use a refractometer to verify the DEF concentration is at the target value of 32.5%.

5. 5

   Check for Exhaust Leaks: Inspect the exhaust system upstream of the sensor. Leaks can introduce excess oxygen, altering the chemical makeup of the exhaust and causing implausible sensor readings.

6. 6

   Software Updates: Check if there is an ECM software update available from Case IH. Manufacturers frequently release software updates to adjust dynamic monitoring thresholds and prevent false codes.

1. 1

   Preparation

   Turn off the vehicle's battery disconnect switch. Ensure the exhaust system has completely cooled to prevent burns.

2. 2

   Removal

   Disconnect the NOx sensor control module's electrical connector. Unclip the connecting cable from all vehicle-specific fixing points.

3. 3

   Extract the Sensor

   Use a specialized NOx/O2 sensor socket (typically 22mm or 7/8") to carefully unscrew the sensor probe from the exhaust pipe bung.

4. 4

   Inspect the Old Sensor

   Check the old sensor head. Black soot indicates oil burning or a rich condition; white crust indicates excessive urea injection or DEF crystallization. If these are present, further engine diagnostics are required to prevent the new sensor from failing.

5. 5

   Clean the Port

   Clean the threads in the exhaust bung. Do not use silicone sprays, oil sprays, or grease, as these will contaminate the new sensor's electrochemical cells.

6. 6

   Installation

   Thread the new NOx sensor probe into the exhaust bung and tighten to the OEM torque specification.

7. 7

   Routing

   Route the new cable exactly as the original. Ensure it is securely clipped, not pinched, and kept away from extreme heat sources.

8. 8

   Reconnection

   Mount the NOx sensor control module and plug in the electrical connector, ensuring the weather seal is intact to prevent water damage.

9. 9

   Reset and Calibration

   Reconnect the battery. Use your diagnostic scan tool to clear the fault codes. Perform any required SCR system resets or NOx sensor adaptations as dictated by the on-board software.

10. 10

    Validation

    Run the engine and monitor live data to ensure the new sensor is broadcasting accurate NOx and oxygen concentrations once it reaches its operating temperature (approx. 800°C).