Systems and methods for controlling a gasoline urea selective catalytic reductant catalyst are described. In one example, an observer is provided that corrects an estimate of an amount of NH.sub.3 that is stored in a SCR. The amount of NH.sub.3 that is stored in the SCR is a basis for generating additional NH.sub.3 or ceasing generation of NH.sub.3.

Various embodiments include a method for regenerating a coated particulate filter arranged in an exhaust-gas duct of a motor vehicle. The method may include: detecting a need for particulate filter regeneration; determining a first diagnosis value before initiating particulate filter regeneration; after determining the first diagnosis value, carrying out particulate filter regeneration; determining a second diagnosis value after particulate filter regeneration; determining a difference between the first determined diagnosis value and the second determined diagnosis value; comparing the determined difference with a threshold value; and identifying a particulate filter defect if the determined difference exceeds the threshold value.

An exhaust treatment device for a diesel engine is provided, which includes a parked regeneration requirement notification component and a parked regeneration start operation component. A regeneration process of the diesel particulate filter (DPF) includes an automatic regeneration process and a parked regeneration process. The automatic regeneration process is automatically started when an estimation value of particulate material (PM) accumulated in the DPF reaches a predetermined automatic regeneration start determination value. The parked regeneration process is performed when first and a second conditions are satisfied. The first condition is that a parked regeneration requirement notification component performs a notification of a parked regeneration requirement when a number of cancellations of the automatic regeneration process reaches a predetermined value. The second condition is that the parked regeneration start operation component is subjected to a start operation during a parked state in which an engine equipped machine is neither traveling nor working.

A method for controlling exhaust gas aftertreatment in an exhaust gas aftertreatment system having at least one nitrogen oxide storage catalyst and at least one catalyst for selective catalytic reduction is provided, wherein, in phases of a high load, a combustion engine is operated with a substoichiometric fuel/air mixture, and nitrogen oxides in the exhaust gas are reduced in the nitrogen oxide storage catalyst to ammonia, which is stored in the catalyst for selective catalytic reduction, and, when the storage capacity of the catalyst for selective catalytic reduction is exceeded, the combustion engine is operated with a superstoichiometric fuel/air mixture, thus allowing nitrogen oxides in the catalyst for selective catalytic reduction to be reduced by the stored ammonia.

Systems and methods for controlling a gasoline urea selective catalytic reductant catalyst are described. In one example, an observer is provided that corrects an estimate of an amount of NH.sub.3 that is stored in a SCR. The amount of NH.sub.3 that is stored in the SCR is a basis for generating additional NH.sub.3 or ceasing generation of NH.sub.3.

Disclosed is a method for diagnosing a first exhaust treatment component for treatment of an exhaust gas stream comprising means for oxidizing nitric oxide into nitrogen dioxide. A first reduction catalytic converter is arranged upstream said means for oxidizing nitric oxide into nitrogen dioxide, and a second reduction catalytic converter is arranged downstream said means. A reagent is for reduction of nitrogen oxides in said first catalytic converter, and a first sensor measures an occurrence of nitrogen oxide downstream said means but upstream said second reduction catalytic converter. The method comprises: causing a supply of reagent upstream said first reduction catalytic converter to an extent exceeding the extent to which reagent is consumed by the first reduction catalytic converter, determining a first measure of the occurrence of reagent downstream said means for oxidizing, and diagnosing said means for oxidizing nitric oxide into nitrogen dioxide based on said first measure.

A system for determining a performance status of an exhaust aftertreatment system may include determining an ammonia-to-nitrogen ratio using a sample ammonia input value and a sample NO.sub.x input value. An actual NO.sub.x input value and an actual ammonia input value can be received. An emission value from may be received from a first sensor. A NO.sub.x emission estimate, an ammonia slip estimate, and an optimal ammonia storage value for a selective catalytic reduction may be determined using an iterative inefficiency calculation based, at least in part, on the actual NO.sub.x input value, the actual ammonia input value, and the ammonia-to-nitrogen ratio; and the NO.sub.x emission estimate, the ammonia slip estimate, and the optimal ammonia storage value may be outputted to a diagnostic system.

A method of calculating a nitrogen oxide (NOx) mass reduced from a lean NOx trap (LNT) during regeneration includes calculating a C3H6 mass flow used to reduce the NOx among a C3H6 mass flow flowing into the LNT of an exhaust purification device, calculating a NH3 mass flow used to reduce the NOx among a NH3 mass flow generated in the LNT, calculating a reduced NOx mass flow based on the C3H6 mass flow used to reduce the NOx and the NH3 mass flow used to reduce the NOx, and calculating the reduced NOx mass by integrating the reduced NOx mass flow over a regeneration period.

A method is provided for ascertaining a NO.sub.x concentration and an NH.sub.3 slip downstream from an SCR catalytic converter of an internal combustion engine of a vehicle. State variables of an internal combustion engine as first input variables and an updated NH.sub.3 fill level of the SCR catalytic converter as a second input variable cooperate with at least one machine learning algorithm or at least one stochastic model. The at least one machine learning algorithm or at least one stochastic model calculates the NO.sub.x concentration and the NH.sub.3 slip downstream from the SCR catalytic converter as a function of the first input variables and the second input variables and output the same as output variables.

An internal combustion engine has an exhaust gas aftertreatment system comprising in the given order in the flow direction of the exhaust gas: a device for metering ammonia and/or a compound that can be decomposed to form ammonia into the exhaust gas to be cleaned, as a reducing agent; one or more SCR catalysts, which form a first SCR unit; one or more SCR and/or ammonia oxidation and/or ammonia slip catalysts, which form a second SCR unit; and a NO.sub.x sensor in the exhaust gas tail pipe. An amount, to be metered into the exhaust gas, of ammonia and/or of the decomposable compound is set using the nitrogen oxide concentration in the exhaust gas tail pipe that is determined by the NO.sub.x sensor, and the occurrence or non-occurrence of an ammonia excess in the region of the NO.sub.x sensor can be determined from the sensor signal of the NO.sub.x sensor by evaluating said sensor signal.