Methods and systems are provided for monitoring a NOx storage capacity of a passive NOx adsorption catalyst (PNA) included in an exhaust gas after-treatment system of an engine. In one example, a method may include, after an engine cold start and prior to an exhaust gas temperature reaching an upper threshold temperature, indicating degradation of the PNA based on an amount of NOx measured downstream of the PNA during a fuel cut event and while the exhaust gas temperature is between a lower threshold temperature and the upper threshold temperature. In this way, degradation of the NOx storage capacity may be inferred based on an amount of NOx released from the PNA and independent of a NOx storage measurement.

Methods and systems are provided for a low temperature NOx adsorber (LTNA). In one example, a method includes initiating a desulfation of an LTNA responsive to an estimated sulfur exposure exceeding a threshold, the desulfation including heating the LTNA to a first threshold temperature while maintaining an exhaust oxygen level above a threshold level throughout the entire desulfation.

A method for diagnosing an aftertreatment component, wherein nitrogen oxide is reduced using a first catalytic converter upstream said aftertreatment component and a second catalytic converter downstream said aftertreatment component, said aftertreatment component oxidizing nitric oxide into nitrogen dioxide. A first sensor measure nitrogen oxide downstream said first catalytic converter but upstream said aftertreatment component, and a second sensor measure nitrogen oxide downstream said aftertreatment component. The method includes: supplying additive upstream said first catalytic converter; using said first and second sensors, performing a first measurement at a first temperature of said first aftertreatment component; using said first and second sensors, performing a second measurement at a second temperature of said first aftertreatment component; and diagnosing oxidation of nitric oxide into nitrogen dioxide in said aftertreatment component using said first and second measurements.

A catalyst deterioration diagnosis method is a method for a system. The system includes a gas sensor having ammonia interference property that measures an air-fuel ratio and nitrogen oxide concentration of an exhaust gas that has passed through a catalyst. Monitoring of temporary increase of nitrogen oxide concentration to be detected by the gas sensor is started, and thereby a temporarily increased amount of the nitrogen oxide concentration is acquired. The monitoring is started when a fuel injection device restarts fuel injection after a fuel cut in a case where an air-fuel ratio most recently obtained by the gas sensor is larger than a predetermined threshold air-fuel ratio. The predetermined threshold air-fuel ratio is larger than a stoichiometric air-fuel ratio. Whether or not the temporarily increased amount is larger than a threshold amount is determined.

Systems, apparatuses, and methods include an upstream exhaust analysis circuit structured to determine a characteristic of an exhaust gas stream entering a nitrous oxide (NOx) storage catalyst; a prediction circuit structured to predict a downstream NOx concentration of an exhaust gas stream exiting the NOx storage catalyst based on a model of a NOx storage capacity or a dynamic response of the NOx storage catalyst; a downstream exhaust analysis circuit structured to determine a downstream NOx concentration of the exhaust gas stream exiting the NOx storage catalyst; and a comparison circuit structured to compare the predicted downstream NOx concentration to the determined downstream NOx concentration, and determine a health of the NOx storage catalyst based on the comparison.

A method for monitoring a gas sensor (14) which comprises two electrochemical measuring cells (20, 30) and which is arranged in an exhaust tract (10) of an internal combustion engine (11), wherein the sensor elements (20, 30) exhibit a substantially identical sensitivity towards a first gas component and a different sensitivity towards a second gas component and are insensitive towards further gas components. In an operating state in which an exhaust gas stream at the gas sensor (14) contains less of the second gas component than of the first gas component a concentration of the first gas component is calculated from each of the sensor signals from the sensor elements (20, 30) and a defect in a sensor element (20, 30) is deduced from the concentrations of the first gas component.

A method for monitoring a nitrogen oxide storage catalyst in an exhaust system of an internal combustion engine, in which a reduction of nitrogen oxides is carried out by means of a reducing agent is disclosed. During a regeneration of the nitrogen oxide storage catalyst, the following steps are carried out: A measurement is carried out, from which a slip rate of the reducing agent not absorbed in the nitrogen oxide storage catalyst is ascertained. In addition, at least one expected value for the slip rate of the reducing agent is ascertained from at least one model. Subsequently, a computation of a monitoring variable is carried out by means of the slip rate of the reducing agent ascertained from the measurement and the at least one expected value for the slip rate of the reducing agent. Finally, a diagnosis of the storage capacity of the nitrogen oxide storage catalyst is carried out on the basis of the monitoring variable.

Improved systems and methods for dosing agent injection adaptation for a selective catalytic reduction (SCR) system of an engine of a vehicle involve an adaptation procedure that is generally divided into distinct phases based upon the requirement to obtain an accurate dosing adaptation. The phases themselves provide the specific functions of catalyst ammonia storage depletion, catalyst ammonia storage and NOx conversion stabilization, and adaptation value factor determination and verification.

Various embodiments may include a method for monitoring a nitrogen oxide trap comprising: monitoring a storage capacity of the nitrogen oxide trap; deactivating nitrogen oxide trap regeneration based on the monitored storage capacity; and upon a predetermined event, reactivating nitrogen oxide trap regeneration.

An exhaust gas control apparatus for an internal combustion engine includes a NO.sub.X storage reduction catalyst, a selective catalytic reduction catalyst, and an electronic control unit configured to shift an operation state of the engine from a rich operation state to a lean operation state, in a case where an acquired temperature of the NO.sub.X storage reduction catalyst is higher than a storage limit temperature, and an acquired NH.sub.3 adsorption amount is equal to or larger than a lower limit adsorption amount when a lean operation restart request is made, and not to shift the operation state from the rich operation state to the lean operation state in a case where the acquired temperature of the NO.sub.X storage reduction catalyst is higher than the storage limit temperature and the acquired NH.sub.3 adsorption amount is smaller than the lower limit adsorption amount when the lean operation restart request is made.