In a method and a device for monitoring the operability of an emission control system of an internal combustion engine, at least two catalytic converters are situated in succession in an exhaust duct. For tracking control, breakthrough detection for diagnosing the first catalytic converter, and for a second balancing for the storage capacity of oxygen or rich gas of the second catalytic converter, a two-point lambda probe be used and, for the latter, tolerance and aging effects are compensated. This results in particular in cost advantages in emission control systems for fulfilling stricter emission and diagnostic requirements.

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 control and evaluation unit for the operation and evaluation of at least one sensor, in particular for the operation and evaluation of at least one lambda probe of an internal combustion engine, signal inputs being disposed for the reception of analog measured signals of the at least one sensor, received analog measured signals being digitized by way of an analog/digital converter, a signal transfer unit, by way of which digitized signals are transferred to a calculation unit, being disposed, and provision being made in particular that the signal inputs are switchable by way of a multiplexer.

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.

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 optical sensor for sensing combustion products avoids fouling and damage to optical components by using a “windowless” design in which an air curtain through an orifice provides a constantly refreshing transparent shield protecting the optical components from corrosive combustion gases and resisting the accumulation of particulates that might otherwise foul a static window.

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.

A diagnostic module for diagnosing a particulate matter sensor in a vehicle includes a sensor mode selection module, a heater power detector, and a protection tube diagnostic module. The sensor mode selection module selects a regeneration mode for the particulate matter sensor from among a plurality of operation modes. The regeneration mode regenerates the particulate matter sensor. The heater power detector determines a voltage output based on a voltage applied to the particulate matter sensor. The voltage output corresponds to operation of the particulate matter sensor in the selected mode. The protection tube diagnostic module performs a diagnostic of the particulate matter sensor. The protection tube diagnostic module selectively diagnoses a fault in the particulate matter sensor based on the voltage output determined during the regeneration mode and a regeneration power threshold.

A control device of an exhaust sensor comprises a cell temperature detecting part detecting a temperature of the electrochemical cell, a heater control part controlling the heater so that a temperature of the electrochemical cell becomes the target temperature, and a judging part judging whether a water repellency of the protective layer is falling. The judging part judges that the water repellency of the protective layer is falling if a condition for judging abnormality is satisfied. The condition for judging abnormality includes a temperature of the electrochemical cell detected by the cell temperature detecting part falling from the target temperature and a speed of fall of the temperature being faster than a speed of fall of the temperature of the electrochemical cell when the heater is turned off.

A sensor element for detecting a physical property of a gas includes: a solid electrolyte film; a first end area and a second end area situated diametrically opposite in the longitudinal direction; a functional element in the first end area in the interior which is electrically conductively connected to a contact surface situated in the second end area on the outer surface, the electrically conductive connection having a strip conductor running essentially in the longitudinal direction in the interior of the sensor element; and a reference gas channel running essentially in the longitudinal direction of the sensor element communicating with a reference gas outside of the sensor element via a reference gas opening, the strip conductor and the reference gas channel being situated in such a way that at least a partial overlap occurs between them.