Various embodiments of the teachings herein include methods for determining the sulfur content in an exhaust tract of a motor vehicle. The method may include: determining a change in the nitrogen oxide abatement efficiency of a coated particulate filter arranged in the exhaust tract and/or a determined ammonia storage capacity change of a coated particulate filter arranged in the exhaust tract; comparing the determined change to a threshold value; identifying an excessive sulfur content if the comparison shows that the determined change exceeds the threshold value; and undertaking one or more corrective actions in response to identifying an excessive sulfur content.

A system includes a controller configured to perform an enable operation responsive to receiving information indicative of an enable parameter, the enable operation includes: determining a predicted downstream NOx value of an exhaust gas stream exiting a NOx storage catalyst; determining a downstream NOx value of the exhaust gas stream exiting the NOx storage catalyst; determining an error between the predicted downstream NOx value and the determined downstream NOx value; comparing the error to an error threshold; and determining that the NOx storage catalyst is in good health responsive to determining that the error does not exceed the error threshold. The controller is further configured to perform a disable operation responsive to receiving information indicative of a disable parameter, the disable operation causing a deactivation of at least a portion of the controller.

Methods and systems are provided for reducing soot sensor electrode degradation in harsh chemical environment introduced as a result of desulfation of a lean NOx trap positioned upstream of the soot sensor. In one example, a method may include in response to the SOx load being higher than the threshold, prior to initiating desulfation of LNT, operating the soot sensor in a pre-desulfation mode where the negative electrode is connected to the positive electrode for a brief duration, while the positive electrode is disconnected from the positive electrode. However during desulfation, when H.sub.2S is released as a by-product, both the electrodes may be open, i.e. not connected to the positive electrode or ground, thereby reducing the possibility of sensor degradation.

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 system includes a controller configured to perform an enable operation responsive to receiving information indicative of an enable parameter, the enable operation includes: determining a predicted downstream NOx value of an exhaust gas stream exiting a NOx storage catalyst; determining a downstream NOx value of the exhaust gas stream exiting the NOx storage catalyst; determining an error between the predicted downstream NOx value and the determined downstream NOx value; comparing the error to an error threshold; and determining that the NOx storage catalyst is in good health responsive to determining that the error does not exceed the error threshold. The controller is further configured to perform a disable operation responsive to receiving information indicative of a disable parameter, the disable operation causing a deactivation of at least a portion of the controller.

A method for operating a petrol engine, in which air is introduced into an exhaust tract through which exhaust gas from the petrol engine can flow, bypassing the petrol engine, includes introducing the air into the exhaust tract at a point arranged downstream of a first three-way catalytic converter arranged in the exhaust tract and upstream of a second three-way catalytic converter arranged in the exhaust tract downstream of the first three-way catalytic converter, while the petrol engine is operated with a sub-stoichiometric combustion air ratio, where a desulphurization of the second three-way catalytic converter is effected.

An engine controller controlling an engine including an occlusion reduction catalyst in an exhaust device includes a fuel injection controller that controls a fuel injection amount of an injector, an EGR controller that controls an EGR device, a sulfur purge determiner that determines whether sulfur purging of the catalyst is to be performed, and a sulfur purge controller that executes sulfur purge control if the sulfur purging is performed. The sulfur purge control involves performing a fuel injection to achieve a rich air-fuel ratio at an inlet of the catalyst and prohibiting the exhaust-gas introduction. The sulfur purge controller executes sulfur-purge standby control when a sulfur-purge standby condition is satisfied, and resumes the sulfur purge control when the condition becomes non-satisfied after starting the sulfur-purge standby control. The sulfur-purge standby control involves performing the fuel injection to nearly achieve a stoichiometric air-fuel ratio and prohibiting the exhaust-gas introduction.

An engine controller controlling an engine including an occlusion reduction catalyst in an exhaust device includes a fuel injection controller that controls a fuel injection amount of an injector, an EGR controller that controls an EGR device, a sulfur purge determiner that determines whether sulfur purging of the catalyst is to be performed, and a sulfur purge controller that executes sulfur purge control if the sulfur purging is performed. The sulfur purge control involves performing a fuel injection to achieve a rich air-fuel ratio at an inlet of the catalyst and prohibiting the exhaust-gas introduction. The sulfur purge controller executes sulfur-purge standby control when a sulfur-purge standby condition is satisfied, and resumes the sulfur purge control when the condition becomes non-satisfied after starting the sulfur-purge standby control. The sulfur-purge standby control involves performing the fuel injection to nearly achieve a stoichiometric air-fuel ratio and prohibiting the exhaust-gas introduction.

A method and system for reducing cycle to cycle variation of an engine is provided. The system may determine fuel injection characteristics and predict a gas burning rate or flame speed based on the fuel injection characteristics. The system may adjust an ignition timing in response to the predicted gas burning rate within the same engine cycle.

Methods and systems are provided for a low temperature NOx adsorber (LTNA). In one example, a method includes operating in a first mode, the first mode including storing exhaust NOx in an LTNA, heating the LTNA until an LTNA outlet temperature reaches a first threshold temperature, and then converting released NOx in a downstream selective catalyst reduction (SCR) device; and operating in a second mode, the second mode including heating the LTNA until the LTNA outlet temperature reaches a second threshold temperature, higher than the first threshold temperature, and converting exhaust NOx in the SCR device.