Various embodiments include a method of ascertaining the oxygen load of a catalytic converter disposed in an exhaust tract of an internal combustion engine with an exhaust gas sensor is disposed downstream of the catalytic converter comprising: generating a signal using the exhaust gas sensor indicating a proportion of nitrogen oxide and/or ammonia in the exhaust gas; and ascertaining the oxygen load of the catalytic converter at least partly on the basis of the signal from the exhaust gas sensor.

A method for diagnosing NOx sensors in an exhaust aftertreatment system includes suspending reductant dosing in an exhaust aftertreatment system; purging a reductant deposit in a selective catalytic reduction (SCR) system of the exhaust aftertreatment system; adjusting at least one of an ignition timing and an engine speed for an engine to adjust an engine out nitrogen oxide (NOx) amount; receiving measured SCR inlet NOx data from a SCR inlet NOx sensor and measured SCR outlet NOx data from a SCR outlet NOx sensor; determining a phase shift between the measured SCR inlet and SCR outlet NOx data; applying the determined phase shift to the SCR outlet NOx data; and determining a diagnostic feature based on the SCR inlet NOx data and the phase shifted SCR outlet NOx data regarding a state of the SCR inlet and outlet NOx sensors.

Provided is a method for diagnosing whether an oxidation catalyst has degraded, based on an output value from one diagnostic sensor with higher accuracy. When a ratio of nitrogen monoxide that is oxidized by a catalyst and discharged downstream of the catalyst as nitrogen dioxide, with respect to nitrogen monoxide contained in an exhaust gas supplied upstream of the catalyst in an exhaust path is defined as a NO conversion rate, a diagnostic sensor configured to output an electromotive force corresponding to the NO conversion rate as a diagnostic output is provided downstream of the catalyst in the exhaust path, and whether the catalyst has degraded beyond an acceptable limit is diagnosed by comparing the diagnostic output with a threshold value predetermined depending on a temperature of the catalyst.

A method to reduce NOx breakthrough and NH3 slip is provided when the SCR system is increasing in temperature and/or increasing exhaust gas mass flow. The method includes the steps of monitoring states of parameters of the exhaust gas upstream of an SCR catalyst where the states of parameters include at least one of the inlet temperature or the exhaust gas mass flow; identifying one of a temperature increase or an increased exhaust gas mass flow at the SCR inlet; identifying a new lower ammonia set-point or storage concentration for the SCR; and identifying the rate of NH3 consumption. The method further includes the step of determining an “intervening phase” a small dosage of DEF is continued during the intervening phase.

A method of diagnosing an engine system including an engine and an exhaust aftertreatment system. The engine system comprises a plurality of replaceable engine system components. The method comprises maintaining a database with component data comprising, for each one of the replaceable engine system components, a deterioration efficiency parameter correlating the deterioration status of the replaceable engine system component to emission reducing efficiency, and a utility component parameter comprising component exchangeability data; determining the deterioration status of each one of the replaceable engine system components; estimating the emission reducing efficiency for each one of the replaceable engine system components in response to the determined deterioration status and the deterioration efficiency parameter; based on known relation between component exchangeability data and the resulting emission reducing efficiency of a potential exchange of the replaceable engine system component, identifying a replaceable engine system component to exchange.

A controller for controlling operation of an aftertreatment system that is configured to treat constituents of an exhaust gas produced by an engine, the aftertreatment system including a selective catalytic reduction (SCR) catalyst, the controller configured to: generate a short-term cumulative degradation estimate of the SCR catalyst corresponding to reversible degradation of the SCR catalyst due to sulfur and/or hydrocarbons based on a SCR catalyst temperature parameter; generate a long-term cumulative degradation estimate of the SCR catalyst corresponding to thermal aging of the SCR catalyst based on the SCR catalyst temperature parameter; generate a combined degradation estimate of the SCR catalyst based on the short-term cumulative degradation estimate and the long-term cumulative degradation estimate; and adjust an amount of reductant and/or an amount of hydrocarbons inserted into the aftertreatment system based on the combined degradation estimate of the SCR catalyst.

A method to control an internal combustion engine having an exhaust duct and an exhaust gas after-treatment system comprising at least one catalytic converter arranged along the exhaust duct; an oxygen sensor housed along the exhaust duct and arranged upstream of said at least one catalytic converter; and a burner suited to introduce the exhaust gases into the exhaust duct upstream of the oxygen sensor the method provides the steps of calculating the thermal power required to reach the nominal operating temperature of said at least one catalytic converter obtained with an objective value of the air/fuel ratio value; and determining both the objective fuel flow rate and the objective air flow rate to be fed to the burner to obtain the thermal power required to reach the nominal operating temperature of said at least one catalytic converter.

A first gas sensor having a first sensor element includes a first protective cover that protects the first sensor element, and a second gas sensor having a second sensor element includes a second protective cover that protects the second sensor element. The first protective cover is coated with an oxidation catalyst for one target component from among a plurality of target components, and the second protective cover is coated with an inert catalyst for the one target component.

A method for diagnosing a NOx sensor is provided. The method includes receiving data indicative of operating conditions of an engine or an aftertreatment system; determining, during a first period of time, that an amount of NOx output from the aftertreatment system satisfies a low NOx operating mode condition; determining, during a second period of time, that operating conditions for ammonia slip are present based on data regarding operation of the aftertreatment system; responsive to the determination that operating conditions for ammonia slip are present, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; comparing a difference between a minimum value from the first period of time and a maximum value from a second period of time to a diagnostic threshold; and responsive to the difference being less than the diagnostic threshold, setting an alert.

Systems and apparatuses include a circuit structured to receive information indicative of a catalyst health, determine a catalyst health management criteria has been met based on the information, determine a catalyst loading based on the information and the catalyst health management criteria being met, and compare the determined catalyst loading to a predetermined loading limit. A notification circuit is coupled to the circuit and structured to provide a notification when the determined catalyst load exceeds the predetermined loading limit.