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Automotive SCR systems for diesel NOx reduction are dimensioned to reduce NOx efficiently in all driving conditions. In this regard the DEF storage and delivery system is developed to operate in a full range of temperatures, voltages, pressures, etc. To allow a control for optimal performance, sensors are added in the system (temperature, level, pressure sensor). Recently, a DEF quality sensor has been added to assure the correct concentration of urea in water in the onboard DEF tank. Now the question is raised how to assure that the DEF quality sensor is operating correctly and is giving an accurate indication of the liquid in the tank. The objective of this study is to define an independent method (PQD) to verify liquid quality, and challenge the signal generated by the DEF quality sensor. This study describes a possible method and the progress on its validation in various automotive driving conditions.

As electronics make their way into the fuel system, a shift in problem solving can be seen. Previously high risk items were tackled mainly through proving component durability and decreasing the statistical odds of the problem occurring. With an electronically controlled system however it is possible and necessary to define degraded modes, in the event that certain components fail, in order to provide at least a limited functionality for the customer. This paper will discuss some different use cases, and how embedded software can be used to improve functionality over a passive system.