Abstract: A system for diagnosing an improper reductant concentration includes: a selective catalytic reduction (SCR) catalyst unit, a doser configured to dose reductant into a chamber of the SCR catalyst unit, a reductant concentration sensor, and a controller. In some embodiments, the controller is configured to: direct the doser to dose the reductant into the chamber of the SCR catalyst unit, based on information received from the reductant concentration sensor, determine a reductant concentration level in the chamber of the SCR catalyst unit, compare a measured system-out NOx value to at least one benchmark value corresponding to the determined reductant concentration level, and determine a status of the reductant dosed by the doser based on the comparison of the measured system-out NOx value to the at least one benchmark value.

Abstract: System and methods for detecting NH3 slip using cross-sensitivity of an NOx sensor may include accessing a temperature value for a catalyst and determining the temperature value for the catalyst exceeds a predetermined value. If the temperature exceeds the predetermined value, a system-out NOx measurement signal from the system-out NOx sensor and an estimated system-out NOx value are used to calculate a delta value. A flag is set indicative of NH3 slip for an exhaust system responsive to an average of delta values for a predetermined period of time exceeding a predetermined value. If the temperature does not exceed the predetermined value, then an average of a plurality of system-out NOx measurement signals can be calculated and a flag is set indicative of NH3 slip responsive to the calculated average for a predetermined period of time exceeding a predetermined value.

Abstract: A system for diagnosing an improper reductant concentration includes: a selective catalytic reduction (SCR) catalyst unit, a doser configured to dose reductant into a chamber of the SCR catalyst unit, a reductant concentration sensor, and a controller. In some embodiments, the controller is configured to: direct the doser to dose the reductant into the chamber of the SCR catalyst unit, based on information received from the reductant concentration sensor, determine a reductant concentration level in the chamber of the SCR catalyst unit, compare a measured system-out NOx value to at least one benchmark value corresponding to the determined reductant concentration level, and determine a status of the reductant dosed by the doser based on the comparison of the measured system-out NOx value to the at least one benchmark value.

Abstract: System and methods for detecting NH3 slip using cross-sensitivity of an NOx sensor may include accessing a temperature value for a catalyst and determining the temperature value for the catalyst exceeds a predetermined value. If the temperature exceeds the predetermined value, a system-out NOx measurement signal from the system-out NOx sensor and an estimated system-out NOx value are used to calculate a delta value. A flag is set indicative of NH3 slip for an exhaust system responsive to an average of delta values for a predetermined period of time exceeding a predetermined value. If the temperature does not exceed the predetermined value, then an average of a plurality of system-out NOx measurement signals can be calculated and a flag is set indicative of NH3 slip responsive to the calculated average for a predetermined period of time exceeding a predetermined value.

Abstract: An aftertreatment system comprises a SCR system, an engine out NOx (EONOx) adjustment system and a controller. The controller is configured to instruct the EONOx adjustment system to adjust an EONOx amount between a high EONOx level for a first predetermined time and a low EONOx level for a second predetermined time when the SCR system is in a diagnostic enabling condition. The controller determines a SCR system out NOx (SONOx) amount. The controller determines an efficiency parameter of the SCR system from the SONOx amount when the EONOx amount transitions from the low EONOx level to the high EONOx level and if the efficiency parameter satisfies a predetermined threshold. In response to the efficiency parameter not satisfying the predetermined threshold, the controller determines that the SCR system has failed.

Abstract: An aftertreatment system comprises a SCR system, an engine out NOx (EONOx) adjustment system and a controller. The controller is configured to instruct the EONOx adjustment system to adjust an EONOx amount between a high EONOx level for a first predetermined time and a low EONOx level for a second predetermined time when the SCR system is in a diagnostic enabling condition. The controller determines a SCR system out NOx (SONOx) amount. The controller determines an efficiency parameter of the SCR system from the SONOx amount when the EONOx amount transitions from the low EONOx level to the high EONOx level and if the efficiency parameter satisfies a predetermined threshold. In response to the efficiency parameter not satisfying the predetermined threshold, the controller determines that the SCR system has failed.