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.

An emissions measurement system capable of providing an accurate, real-time measurement of an emissions sample is disclosed. The exhaust may be generated by an internal combustion engine, in which case the system may be sequentially connected to the exhaust from the internal combustion engine. The emissions measurement system can include a laser light opacity sensor, a light scattering sensor, and a particle ionization sensor.

A dilution gas mixing unit that is used in an exhaust gas analysis system that analyzes the mixed gas obtained by diluting an exhaust gas with the dilution gas, and mixes the dilution gas with the exhaust gas is provided with a dilution gas supply pipe that is connected to an exhaust gas introduction pipe into which the exhaust gas is introduced and supplies the dilution gas to the exhaust gas introduction pipe, a dilution gas sampling unit that is provided in the dilution gas supply pipe and collects the dilution gas, and a backflow prevention member that is provided closer to the exhaust gas introduction pipe than the dilution gas sampling unit in the dilution gas supply pipe and prevents the mixed gas from flowing backward through the dilution gas supply pipe.

A gas sensor element (10) which includes an element body portion (100); a pump cell (110) which is configured to adjust a concentration of oxygen in a gas to be measured which is introduced into the element body portion (100); a detection chamber (160) which is formed inside the element body portion (100) and into which the gas to be measured in which the concentration of oxygen has been adjusted is introduced; and a layer-shaped cathode electrode (133) which is housed in the detection chamber (160) and configured to decompose NO. A relationship between a volume V1 of the detection chamber (160) and a volume V2 of the cathode electrode (133) in the gas sensor element (10) satisfies either one of conditions (A) and (B) as defined herein.

A gas sensor assembling method includes a step for placing an element dummy such that it has a longitudinal direction in a vertical direction, wherein the cross-sectional shape of the dummy is similar to the cross-sectional shape of a sensor element, a step for fitting a through hole in an annularly-mounted member to the dummy from above vertically, wherein the through hole included in the annularly-mounted member corresponds to the cross-sectional shape of the sensor element, a step for fitting a tubular member to an outer periphery of the annularly-mounted member from above vertically, an step for placing the sensor element in contact with an upper end portion of the dummy on a single straight line, and an step for descending the dummy downwardly vertically for descending the sensor element and fitting the through hole in the annularly-mounted member to the sensor element.

A system and approach for catalyst model parameter identification with modeling accomplished by an identification procedure that may incorporate a catalyst parameter identification procedure which may include determination of parameters for a catalyst device, specification of values for parameters and component level identification. Component level identification may be of a thermal model, adsorption and desorption, and chemistry. There may then be system level identification to get a final estimate of catalyst parameters.

An apparatus includes a dosing module structured to suspend dosing in an exhaust aftertreatment system; a selective catalytic reduction (SCR) inlet NOx module structured to interpret SCR inlet NOx data and an SCR inlet temperature; a SCR outlet NOx module structured to interpret SCR outlet NOx data; and a system diagnostic module structured to determine an efficiency of a SCR system based on the SCR inlet and outlet NOx data over a range of SCR temperatures, wherein the system diagnostic module is further structured to determine a state of at least one of a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and the SCR system based on the SCR efficiency at an elevated SCR temperature range and the SCR efficiency at a relatively lower SCR temperature range relative to a high SCR efficiency threshold and a low SCR efficiency threshold.

An inner protective cover 130 of a gas sensor forms an element-chamber inlet 127 having a first outside opening 128a, a second outside opening 128b, and an element-side opening 129. The second outside opening 128b is disposed such that the path of a measurement-object gas from the first outside opening 128a to the element-side opening 129 of the element-chamber inlet 127 communicates in the middle thereof with a first gas chamber 122, and that there is a path shorter than the shortest path of the measurement-object gas extending from an outer inlet 144a through the first outside opening 128a to a gas inlet 111.

A gas sensor 100 includes a sensor element 110 having a gas inlet 111; an inner protective cover 130 which has a sensor element chamber 124 thereinside and in which an element-chamber inlet 127 and an element-chamber outlet 138a are arranged; and an outer protective cover 140 including a body portion 143, which has a cylindrical shape and in which an outer inlet 144a is arranged, and a front end portion 146, which has an inner diameter smaller than that of the body portion 143 and in which an outer outlet 147a is arranged. The outer inlet 144a includes a horizontal hole 144b arranged in a side portion 143a of the body portion 143 of the outer protective cover 140. The outer outlet 147a is not arranged in a side portion 146a of the front end portion 146 of the outer protective cover 140.

An O.sub.2 sensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes, while the solid electrolyte layer is interposed between the electrodes. The O.sub.2 sensor outputs an electromotive force signal in response to an air-to-fuel ratio of exhaust gas of an engine, which serves as a sensing subject. A constant current circuit, which induces a flow of a predetermined constant electric current between the pair of electrodes of a sensor element, and a current sensing arrangement, which senses a current value of an actual electric current that is conducted through the sensor element, are provided. A microcomputer determines whether an abnormality of the constant current circuit is present based on the current value of the electric current, which is sensed with the current sensing arrangement, in a case where the constant current is induced by the constant current circuit.