A method (200) for ascertaining a catalytic converter state is proposed, wherein an exhaust-gas catalytic converter (130) is monitored on the basis of a catalytic converter model. Here, the catalytic converter model is adapted (250) in a manner dependent on measured values detected by means of one or more sensors (145, 147), wherein a frequency and/or a degree of the adaptation of the catalytic converter model is detected (260). The catalytic converter state is ascertained (270) as non-critical if the frequency and/or the degree of the adaptation do not exceed a predeterminable threshold value or is ascertained (270) as critical if the frequency and/or the degree of the adaptation exceed the predeterminable threshold value.

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.

An abnormality determination apparatus for an ammonia sensor is usable in an exhaust purification system including a catalyst, a supply apparatus, an ammonia sensor, an NO.sub.X sensor, and an oxygen sensor. During a continuation period within which ammonia supply to the catalyst continues after the supply apparatus stops supply of reductant, the abnormality determination apparatus calculates the ammonia concentration on a downstream side of the catalyst as a first concentration value, based on an output of the ammonia sensor and an output of the oxygen sensor. During the continuation period, the abnormality determination apparatus calculates the ammonia concentration on the downstream side of the catalyst as a second concentration value, based on an output of the NO.sub.X sensor and the output of the oxygen sensor. The abnormality determination apparatus determines presence or absence of abnormality in the ammonia sensor based on the first concentration value and the second concentration value.

A method for ascertaining a fill level of at least one exhaust-gas component, which can be stored in a catalytic converter and which is generated in a combustion process, in the catalytic converter, wherein a variation of the fill level of the at least one exhaust-gas component in the catalytic converter during the combustion process is determined, wherein, during time periods in which the combustion process is not operated, a diffusion-induced change of the fill level of the at least one exhaust-gas component in the catalytic converter is determined, and wherein, on the basis of the determined variation during the combustion process and the diffusion-induced change, a fill level of the at least one exhaust-gas component in the catalytic converter is ascertained. The invention furthermore relates to a processing unit and to a computer program for carrying out such a method.

The present disclosure describes methods for evaluating quality of DEF dosed to an EAS including a close coupled SCR unit a downstream SCR unit. A NOx conversion efficiency of the close coupled SCR unit and a NOx conversion efficiency of the downstream SCR unit are used to evaluate quality of DEF. In some embodiments, the NOx conversion efficiency of close coupled SCR unit is used to evaluate quality of DEF. Operation of an EAS using the results of the evaluation of quality of DEF are described.

A system and approach for catalyst model parameter identification with modeling accomplished by an identification procedure that may incorporate a catalyst parameter identification procedure which may include determination of parameters for a catalyst device, specification of values for parameters and component level identification. Component level identification may be of a thermal model, adsorption and desorption, and chemistry. There may then be system level identification to get a final estimate of catalyst parameters.

There is provided an exhaust gas purification system including: a NOx storage-reduction catalyst that is provided in an exhaust system of an internal combustion engine to reduce and purify NOx in exhaust gas; a degree of deterioration estimation module 120 for estimating a degree of deterioration of the NOx storage-reduction catalyst; a regeneration control unit 100 for executing a regeneration process in which exhaust gas is enriched so as to restore a NOx storage capacity of the NOx storage-reduction catalyst; an interval setting module for setting a target interval from an end of the regeneration process to a start of the subsequent regeneration process by the regeneration control unit; and an interval target value correction module for correcting the target interval based on the degree of deterioration that is estimated by the degree of deterioration estimation module.

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.

The present disclosure describes methods for evaluating quality of DEF dosed to an EAS including a close coupled SCR unit a downstream SCR unit. A NOx conversion efficiency of the close coupled SCR unit and a NOx conversion efficiency of the downstream SCR unit are used to evaluate quality of DEF. In some embodiments, the NOx conversion efficiency of close coupled SCR unit is used to evaluate quality of DEF. Operation of an EAS using the results of the evaluation of quality of DEF are described.