The invention relates to a method, system, and computer program product for diagnosing an exhaust gas processing configuration for a combustion engine of a vehicle, said configuration comprising two SCR-units, two NOx-sensors and two reducing agent dosing units suitably arranged, comprising the steps of: performing a series of reducing agent dosing operations by a first reducing agent dosing unit; comparing measured NOx-contents measured by a first NOx-sensor and a second NOx-sensor related to said operations; and if the respective NOx-content measured by the respective NOx-sensors during the performed reducing agent dosing operations are substantially equal, determining that the respective NOx-sensors provide a proper performance.

Various embodiments include a method of operating a diesel engine having an exhaust tract and an SCR-combined diesel particulate filter in the exhaust tract, wherein an aqueous urea solution is introduced into the exhaust tract, and an exhaust gas recirculation apparatus having an exhaust gas recirculation conduit branching off downstream of the SCR-combined diesel particulate filter for performing a low-pressure exhaust gas recirculation comprising: measuring an NH.sub.3 concentration in exhaust gas downstream of the SCR-combined diesel particulate filter; and upon exceeding a threshold value of the measured NH.sub.3 concentration, reducing the low-pressure exhaust gas recirculation rate based at least in part on the measured NH.sub.3 concentration.

A method for operating an exhaust system of an internal combustion engine of a motor vehicle, in which exhaust gas from the internal combustion engine flows through a first SCR catalytic converter, which is followed by an ammonia barrier catalytic converter, and flows through a second SCR catalytic converter which is disposed downstream of the ammonia barrier catalyst, includes introducing a reducing agent introduced into the exhaust gas by a first metering device upstream of the first SCR catalytic converter and by a second metering device upstream of the second SCR catalytic converter. When a predetermined threshold value of a temperature of a region of the exhaust system is exceeded, a quantity of reducing agent introduced into the exhaust gas by the first metering device is increased.

A computer implemented method for anomality detection at a first nitrogen oxide (NOx) sensor forming part of an exhaust gas aftertreatment system (EATS) is provided. The EATS is coupled downstream of an internal combustion engine (ICE). The disclosed methodology applies manipulation of the ICE for detecting such a possible anomality.

Embodiments are directed towards controlling uncontrolled release of ammonia from an engine of a vehicle. An estimated status of the engine is determined prior to an event, such as an estimated load on the engine prior to the vehicle going up a hill. A predictive model of uncontrolled ammonia release is generated for the estimated status. At least one engine-related countermeasure is selected based on the predictive model. If the predictive model of uncontrolled ammonia release with the selected countermeasures satisfies a threshold condition, then the selected engine-related countermeasure is employed.

An internal combustion engine, with an engine regulating device and an exhaust gas aftertreatment device with an SCR catalytic converter for the reduction of at least one NO.sub.x component, and with a catalytic converter regulating device, wherein the engine regulating device is prescribed a target value for an NO.sub.x mean value of the NO.sub.x component of the exhaust gases, which mean value results at an outlet point of the exhaust gas aftertreatment device in relation to a predefinable time period, and the engine regulating device is configured at least in one operating mode to continuously calculate an NO.sub.x reference value for the catalytic converter regulating device with consideration of No.sub.x components which have already been emitted and the predefined target value, which reference value is selected in such a way that the predefined target value results at the outlet point of the exhaust gas aftertreatment device at the end of the predefinable time period when the calculated NO.sub.x reference value of the catalytic converter regulating device is fed as NO.sub.x setpoint value to the regulating means.

A method for ascertaining an exhaust gas composition of an exhaust gas of an internal combustion engine with regard to an ammonia fraction and a nitrogen oxides fraction in an exhaust gas system including an SCR catalytic converter. The method includes detecting, using a sensor, a first signal whose magnitude is a function of the nitrogen oxides fraction of the exhaust gas upstream from the SCR catalytic converter, detecting using a sensor a second signal whose magnitude is a function of the ammonia fraction and the nitrogen oxides fraction of the exhaust gas downstream from the SCR catalytic converter, storing the two signals over an observation period, and ascertaining the ammonia fraction and optionally the nitrogen oxides fraction of the exhaust gas downstream from the at least one SCR catalytic converter using a calculation rule that uses the two signals during the observation period as input variables.

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.

Methods and systems for improving NOx conversion efficiency of a selective catalytic reduction catalyst are described. In one example, an amount of NH.sub.3 stored in a SCR is adjusted after stopping an engine so that a desired amount of NH.sub.3 may be stored within the SCR when the engine is restarted.

A controller 1 includes a calculation unit 10 that receives the current sensor value A1 of the vehicle and calculates an injection amount based on the current sensor value A1 and a target value of the ammonia adsorption amount of the selective reduction catalyst 105 so that the ammonia adsorption amount approaches the target value, and a prediction unit 20 that receives the current sensor value B1 and calculates a corrected target value by future prediction based on the current sensor value B1. The calculation unit 10 calculates the injection amount based on the corrected target value calculated by the prediction unit 20.