Inlet And Outlet Nox Sensor Readings are crucial for monitoring and maintaining the efficiency of a diesel truck’s aftertreatment system. These readings provide valuable insights into the performance of the Selective Catalytic Reduction (SCR) system, which is responsible for reducing harmful nitrogen oxide (NOx) emissions. This article delves into interpreting these readings and understanding their significance.
Decoding NOx Sensor Data
A recent forum post highlighted a series of aftertreatment readings from a 2017 X15 Cummins engine. Let’s break down each parameter and its potential implications:
1. Aftertreatment Outlet NOx Reading: Initially displaying “Not Available,” this reading becomes stable once the SCR temperature reaches around 450 degrees Fahrenheit. This indicates that the sensor requires a specific operating temperature to function correctly.
2. Aftertreatment Outlet NOx Corrected: This value appears when both the SCR inlet and outlet temperatures stabilize around 450 degrees Fahrenheit. It represents the adjusted NOx level after the SCR system has performed its reduction function. A “0” reading suggests effective NOx conversion.
3. Aftertreatment Outlet NOx (Raw): This is the uncorrected reading directly from the sensor, typically around 139 ppm in the example. While it might differ slightly from the corrected value, large discrepancies could indicate sensor issues. During an active SCR test with DEF injection, healthy systems often show values between 60-70 ppm.
4. Aftertreatment SCR Intake/Outlet Temperature: Readings of 295 and 256 degrees Fahrenheit, respectively, suggest the SCR system is in a warm-up phase. These temperatures are normal during this stage.
5. Aftertreatment SCR Intake/Outlet Temperature Signal Voltage: While the example shows “0v,” this likely represents a momentary reading during data logging. Stable voltage readings are crucial for accurate temperature measurements.
6. Aftertreatment Diesel Particulate Filter (DPF) Operating State: An “Inactive” state indicates the DPF is not currently performing a regeneration cycle. This is typical when the engine is operating under normal conditions.
7. Aftertreatment Diesel Particulate Filter Ash Load: A reading of 52.6% suggests accumulated ash in the DPF. Although the original poster noted previous readings of 0%, this parameter reflects mileage-based ash accumulation. Resetting this value requires a specific procedure within the advanced ECM data and should only be performed after physically cleaning the DPF through baking and de-ashing. Incorrectly resetting this value can lead to inaccurate pressure readings and potential ECM malfunctions.
Conclusion
Monitoring inlet and outlet NOx sensor readings, along with other aftertreatment parameters, is essential for maintaining optimal diesel engine performance and minimizing emissions. Understanding these readings allows for proactive identification of potential issues and ensures efficient operation of the SCR and DPF systems. Remember, consulting official service documentation for your specific engine model is crucial for accurate diagnostics and maintenance procedures. Regular maintenance and proper interpretation of these readings contribute significantly to the longevity and efficiency of your diesel truck.
