Methods and systems are provided for adjusting an ammonia (NH.sub.3) sensor output using readings of a nitrogen oxide (NOx) sensor, the NOx sensor having a sensitivity factor to NH.sub.3. In one example, a method may include determining and updating a gain value of the NH.sub.3 sensor during zero NOx conditions to be used to calculate a corrected NH.sub.3 sensor output value, and determining and updating an offset value of the NH.sub.3 sensor during zero NH.sub.3 conditions to be used to zero the NH.sub.3 sensor during zero NOx conditions.

Systems and methods for controlling a gasoline urea selective catalytic reductant catalyst are described. In one example, an observer is provided that corrects an estimate of an amount of NH.sub.3 that is stored in a SCR. The amount of NH.sub.3 that is stored in the SCR is a basis for generating additional NH.sub.3 or ceasing generation of NH.sub.3.

In a control apparatus, a heater adjuster performs a regeneration task of causing a heater to heat a sensing member of a particulate matter sensor to burn particulate matter deposited on the sensing member to thereby remove the particulate matter from the sensing member. The heater adjuster performs a deposition reduction task of maintaining, for a predetermined duration, a temperature of the sensing member at a deposition reduction temperature that reduces additional particulate-matter deposition on the sensing member. The predetermined duration is defined from completion of a regeneration task to a time when an environmental condition around the particulate matter sensor is determined to be stable. The heater adjuster stops the heater from heating the sensing member if a condition determiner determines that the environmental condition around the particulate matter sensor is stable.

Methods and systems for monitoring a NOx sensor for a NOx offset value are described. In one example, the NOx offset value may be based on a minimum NOx concentration observed over an entire drive of a vehicle. The NOx offset monitor may be inhibited in response to inferring or detecting a presence of NH.sub.3 in an exhaust system.

A control module for an aftertreatment system that includes a selective catalytic reduction (SCR) catalyst and an oxidation catalyst, comprises a controller configured to be operatively coupled to the aftertreatment system. The controller is configured to determine an actual SCR catalytic conversion efficiency of the SCR catalyst. The controller determines an estimated SCR catalytic conversion efficiency based on a test sulfur concentration selected by the controller. In response to the estimated SCR catalytic conversion efficiency being within a predefined range, the controller sets the test sulfur concentration as a determined sulfur concentration in a fuel provided to the engine. The controller generates a sulfur concentration signal indicating the determined sulfur.

A method for determining a reference value of a presence of at least one substance (NO.sub.x) occurring in an exhaust gas stream of an internal combustion engine (101), wherein the at least one substance is subjected to exhaust treatment, the exhaust treatment being carried out in dependence on the reference value (Em.sub.ref; Em.sub.ref,1; Em.sub.ref,2) When the internal combustion engine (101) is started: accumulating the occurrence (Em.sub.ACC,1; Em.sub.ACC,2) of the at least one substance (NO.sub.x) downstream from the exhaust treatment during a first period, and determining whether to redetermine the reference value (Em.sub.ref; Em.sub.ref,1; Em.sub.ref,2) based on the accumulated occurrence (Em.sub.ACC,1; Em.sub.ACC,2) of the at least one substance (NO.sub.x).

A method to control a burner for an exhaust system of an internal combustion engine with an exhaust gas after-treatment system including at least one catalytic converter. The method provides the steps of calculating the thermal power needed to reach the nominal operating temperature of the at least one catalytic converter and determining an actual number of revolutions with which to operate a fresh air pumping device based on the sum of a nominal number of revolutions, a closed-loop contribution of the number of revolutions with which to operate the fresh air pumping device, and a further contribution of the number of revolutions with which to operate the fresh air pumping device in order to ensure optimal thermal power exiting the burner.

A system and method for reducing the nitrogen oxides found in the exhaust produced by a vehicle engine, the system comprising a NOx trap and a first adding means for adding a reducing agent to the exhaust gas. The first adding means is positioned downstream of the engine and either upstream of or within the NOx trap.

In a method and device for controlling and/or monitoring the function of a secondary air supply in an emission control system of an internal combustion engine, the emission control system includes at least two catalytic converters situated in succession in an exhaust duct, it being possible for the second catalytic converter to be implemented as a combination of catalytic converter and particulate filter. For a secondary air diagnosis and for secondary air control, a two-point lambda probe is situated, with respect to a direction of flow of exhaust gas, downstream of the first catalytic converter. Measures are applied for compensating tolerance and aging effects of the two-point lambda probe. This results in particular in cost advantages in emission control systems for fulfilling stricter emission requirements. In particular, this makes it possible to operate the particulate filter in optimized fashion.

An exhaust aftertreatment system including a selective catalytic reduction device (SCR), a NOx sensor and a reductant injection system is described. A method for controlling the reductant injection system to inject reductant into the exhaust gas feedstream upstream relative to the SCR includes monitoring engine operation, and determining an initial reductant dosing rate responsive to the engine operation. A dosing perturbation is induced in the reductant dosing rate. The exhaust gas feedstream is monitored via the NOx sensor, and a reductant dosing correction term is determined based upon the monitoring. A final dosing rate for controlling the reductant injection system is determined based upon the initial reductant dosing rate, the dosing perturbation, and the reductant dosing correction term