Methods and/or systems for operating an exhaust-gas aftertreatment system of an internal combustion engine include: setting the internal combustion engine to a diagnostic operating mode with relevant diagnostic operating parameters of the internal combustion engine are set to correspond with diagnostic default values; inducing a targeted, defined NH.sub.3 and/or NO.sub.X concentration change upstream of the filter; measuring the NH.sub.3 and/or NO.sub.X concentration change downstream of the filter; providing a correlating concentration comparison value; evaluating the concentration change on the basis of the respective concentration comparison value and predefined limit values; and diagnosing the SCR particle filter as defective if the evaluation yields that the concentration comparison value has overshot a predefined limit value.

A diesel-emissions reduction unit having an inlet adapted to receive an exhaust stream of the diesel engine; a diesel oxidation trap catalyst located adjacent the inlet; a dosing controller and an injection lance arranged to meter aqueous NH.sub.3 into the exhaust stream; a NOx concentration sensor and a NH.sub.3 concentration sensor with at least one oxidation catalyst panel arranged to isolate the NOx concentration sensor from NH.sub.3 in the exhaust stream; and an exhaust heater arranged to heat the exhaust stream of the diesel engine toward the inlet of the diesel emissions reduction unit.

Systems, apparatuses, and methods include a controller for an exhaust aftertreatment system including a SCR catalyst in exhaust gas-receiving communication with an engine and at least one reductant dosing system structured to provide reductant to the exhaust gas. The controller is structured to determine a concentration of one or more of NO and NO.sub.2 at or proximate an inlet of the exhaust aftertreatment system and based on a dynamic model of the SCR catalyst, information indicative of a concentration of NOx at or proximate an outlet of the exhaust aftertreatment system, and information indicative of an amount of stored reductant in the SCR catalyst. The controller is further structured to command the at least one reductant doser to increase, decrease, or maintain an amount of reductant provided to the exhaust gas based on the determined concentration of one or more of NO and NO.sub.2 in the exhaust gas.

A catalyst deterioration diagnosis method is a method for a system. The system includes a stepped transmission or a continuously variable transmission connected to an internal combustion engine, a catalyst into which an exhaust gas from the internal combustion engine is introduced, and a gas sensor having sensitivity to ammonia that outputs a detection value corresponding to a component of an exhaust gas that has passed through the catalyst. The catalyst deterioration diagnosis method includes the following steps. Monitoring of temporary increase of a detection value of the gas sensor is started, and thereby a temporarily increased amount of the detection value of the gas sensor is acquired. The monitoring is started when upshifting of the stepped transmission or pseudo-upshifting of the continuously variable transmission is performed. Whether or not the temporarily increased amount is larger than a threshold amount is determined.

A method includes acquiring nitrogen oxide (NOx) data indicative of a first amount of NOx in an exhaust flow exiting an engine and a second amount of NOx in the exhaust flow exiting an exhaust aftertreatment system coupled to the engine where the exhaust aftertreatment system including a selective catalytic reduction (SCR) system including a SCR catalyst; determining a NOx conversion efficiency fault is present within the exhaust aftertreatment system based on the first amount of NOx and the second amount of NOx; monitoring an actual amount of NOx in the exhaust flow downstream of the SCR catalyst; determining an expected amount of NOx downstream of the SCR catalyst; and determining the SCR catalyst is responsible for the NOx conversion efficiency fault in response to the actual amount of NOx differing from the expected amount of NOx by more than a threshold amount.

Methods and systems are provided for operating an engine of a vehicle. In one example, a method may include positioning an oxygen sensor in an engine exhaust downstream from a selective catalytic reduction (SCR) catalyst, determining an oxygen storage capacity of the SCR catalyst based on a measurement of the oxygen sensor, and determining an extent of deactivation of the SCR catalyst based on the oxygen storage capacity

A method of monitoring an SCR catalyst in which an area factor (a) of the SCR catalyst is ascertained by means of an observer. It is concluded that there is a fault in the SCR catalyst when a comparison shows that the area factor (a) has gone below a threshold value (S).

An aftertreatment system configured to reduce constituents of an exhaust gas produced by an engine comprises an aftertreatment component and an optical assembly. The optical assembly comprises an optical emitter configured to emit light onto a face of the aftertreatment component, and an optical detector configured to detect light reflected from the face of the aftertreatment component. A controller is configured to determine at least one of an amount of NOx gases or an amount of ammonia on the face of the aftertreatment component based on an optical parameter of the detected light that has reflected from the face of the aftertreatment component.

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.