Abstract: Apparatus and methods for measuring NOx concentrations are disclosed. One method includes the steps of providing a gas stream having a NO concentration and a NO2 concentration, wherein a sum of the NO concentration and the NO2 concentration is a total NOx concentration; contacting the gas stream with a first zirconium oxide based oxygen sensor at a first temperature to achieve a first NO:NO2 equilibrium at the first temperature; contacting the gas stream with a second zirconium oxide based oxygen sensor at a second temperature to achieve a second NO:NO2 equilibrium at the second temperature; and determining the total NOx concentration by measuring a response of the first zirconium oxide based oxygen sensor to achieve the first NO:NO2 equilibrium and a response of the second zirconium oxide based oxygen sensor to achieve the second NO:NO2 equilibrium. The second temperature is different than the first temperature.

Abstract: A gas sensor extending along an axial direction, the gas sensor including: a housing having a through hole, the through hole including an expanding portion at a leading end thereof; a gas sensing element inserted into the housing, having a closed leading end, and provided with a sensor electrode on an outer surface of the leading end side thereof; a heater inserted into the gas sensor, and including a contact portion where the heater contacts an inner surface; an protector fixed on the leading end side of the housing and having an outer protector including an outer air hole and an inner protector being positioned within the outer protector and spaced apart from the outer protector in the radial direction; and an inner air vent provided between the inner protector and the leading end of the housing.

Abstract: A gas sensor apparatus 3 in an air-fuel ratio detection system 1 includes a gas sensor element 4 which outputs a detection signal corresponding to air-fuel ratio, and a gas sensor control circuit 2 which includes a detection section 20 for outputting a first output signal VIP1, a second output signal VIP2, and a third output signal VIP3 in accordance with the detection signal. This detection section 20 outputs the first output signal VIP1 which changes in accordance with the air-fuel ratio at least within a wide first air-fuel ratio zone, the second output signal VIP2 which changes in accordance with the air-fuel ratio within a narrow zone in the vicinity of the stoichiometric ratio, and the third output signal VIP3 which changes in accordance with the air-fuel ratio within a narrow zone in the lean region.

Abstract: A sensor element of a gas sensor, which is used for determining the concentration of ammonia and, optionally, at least one further component of a gas mixture, in particular in exhaust gases of combustion engines. The sensor element includes at least one first auxiliary electrode and at least one measuring electrode positioned downstream in the flow direction of the gas mixture, which are in direct contact with the gas mixture, a signal generated by the measuring electrode being used at least intermittently for determining the concentration of ammonia. A potential, at which ammonia contained in the gas mixture is oxidized, is applied at least intermittently to the first auxiliary electrode or the measuring electrode.

Abstract: A gas sensor diagnostic method includes the steps of counting the reversal number of times that a target air-fuel ratio for an air-fuel mixture to be supplied to an internal combustion engine reverses from a rich side to a lean side or from the lean side to the rich side through a specific air-fuel ratio defined as a boundary of the rich and lean sides; obtaining a detection signal of a gas sensor at constant time intervals during a diagnosis period between a timing when the count for the reversal number is started and a timing when the reversal number reaches a predetermined number; calculating a moderated signal by applying a moderation calculation using a predetermined moderation coefficient to the obtained detection signal; calculating a deviation between the obtained detection signal and the calculated moderated signal; and determining whether the gas sensor is in an abnormal state or not on the basis of the deviation.

Abstract: A gas concentration measuring apparatus for use in air-fuel ratio control of motor vehicle engines is provided which is designed to select or determine a correction factor for an output of an A/F sensor, as produced through a sensor control circuit, for compensating for errors in circuit characteristics of the A/F sensor and/or the sensor control circuit to ensure the accuracy of measurement in the apparatus.

Abstract: In a method for determining an air fuel ratio of an internal combustion engine on the basis of an ion current, for detecting an ion current generated per ignition within a combustion chamber of the internal combustion engine, the method measures a generation period in which the ion current is greater than a determination value set as long as the ion current is generated, computes a divisor for computing a rate of fluctuation of the generation period of the ion current on the basis of a plurality of measured generation periods, computes the rate of fluctuation of the generation period of the ion current by weighing in a direction of increasing the computed divisor, and determines that an air fuel ratio is excessively high in the case that the calculated rate of fluctuation is equal to or more than a predetermined value.

Abstract: A cylinder deviation of an actual air-fuel ratio before an air-fuel-ratio dither control is obtained based on a variation of an actual air-fuel ratio by the dither control, a variation amount of detected air-fuel ratio, and a cylinder deviation of detected air-fuel ratio before the dither control. A cylinder deviation of actual air-fuel ratio of each cylinder is accurately estimated. When the number of times in which the cylinder deviation of air-fuel ratio exceeds a decision value is greater than a predetermined number, it is determined that an abnormality occurs in the cylinder.

Abstract: A gas sensor having a gas sensor element which includes: a reference electrode; a solid electrolyte layer having oxygen ion conductivity; a detection electrode; and an electrode-protecting layer covering the detection electrode. The electrode-protecting layer is a porous body carrying catalytic metal, and includes: a detection electrode side portion having a catalytic metal loading ratio of more than 0% by weight and not more than 0.005% by weight; and a surface side portion provided closer to the outer surface of the electrode-protecting layer than the detection electrode side portion, the surface side portion having a catalytic metal loading ratio of 0.01% by weight or more.

Abstract: A gas sensor has a sensor element detecting a concentration of a specified gas, a housing fixing this element to a gas pipe to expose it to measuring-gas flow, and cylindrical inner and outer covers of a different radius, configured in concentric configuration, having a base part. Side surface openings are formed in the inner cover so that each opening turns upward from the outside to the inside of the inner cover. Openings are formed in the bottom surface of the inner cover around a circle in concentric with the inner cover. Openings are formed in the side surface of the outer cover through which the measuring gases are introduced into a gap between the inner and outer covers. A gap is formed between bottom surfaces of both the covers. An opening is formed at the center of the bottom surface of the outer cover.

Abstract: It is an object of the present invention to provide a gas concentration detection apparatus that is capable of forming an accurate activity judgment when a gas concentration detection cell begins to detect gas concentration with high accuracy. When warm-up begins at time t0 in a NOx concentration detection apparatus that achieves NOx concentration detection with a NOx sensor cell after excess oxygen is discharged by an oxygen pump cell, a NOx sensor cell output begins to rise at time t1. Subsequently, at time t2, an oxygen pump cell output begins to rise. An inflection point appearing in the NOx sensor cell output is then located. At time t5 at which the inflection point appears, an activity judgment about the NOx sensor cell is formed.

Abstract: A gas sensor includes a first space for a measurement gas from a gas-introducing hole via a first diffusion rate-determining section, a main pumping means for controlling a partial pressure of oxygen in the measurement gas introduced into the first space to have a predetermined value, a second space for the measurement gas from the first space via a second diffusion rate-determining section, and a measuring pumping means for reducing or decomposing a NOx component in the measurement gas introduced from the second space via a third diffusion rate-determining section so that oxygen produced thereby is pumped out to detect a current generated by pumping out the oxygen. A ratio (Wc/We) between a width (We) of an end of a sensor element and a width (Wc) of the gas-introducing hole is not less than 0.3 and less than 0.7.

Abstract: The present invention provides, as one aspect, a signal processor for a gas sensor that is disposed in an exhaust passage of an internal combustion engine and senses concentration of a specific component in exhaust gas. The signal processor includes a calculation unit that performs moderation operation at every instant for a sensor output of the gas sensor, an evaluation unit that evaluates a degree of pressure variation impact on the sensor output caused in the exhaust passage, and a change unit that changes a mode of the moderation operation according to a result of the evaluation by the evaluation unit.

Abstract: An interface device for a gas sensor includes a detection resistor having first and second ends to generate voltages by a current output of the gas sensor, a differential amplifier having first and second input terminals to receive the voltages of the first and second resistor ends and an output terminal to output a voltage according to a difference between the voltages of the first and second resistor ends, a first switching element to transmit the voltage of the first resistor end to the first input terminal of the differential amplifier in a transmission state and interrupt transmission of the voltage of the first resistor end to the first input terminal of the differential amplifier in an interruption state and a second switching element turned on to establish continuity between the first and second input terminals of the differential amplifier when the first switching element is in the interruption state.

Abstract: A gas sensor diagnostic method (or apparatus) is arranged to periodically obtain sensor output values of a gas sensor such as an oxygen sensor for an internal combustion engine, and to determine local extreme values from the sensor output values obtained during a period of interruption of fuel supply to the engine. Moreover, the local extreme values are compared with a first predetermined threshold level. When the number of the local extreme values reaches a predetermined first number, a diagnosis is performed to determine whether the gas sensor is in an improper condition or not, in accordance with results of the comparison of the local extreme values with the first threshold level.

Abstract: Systems and methods for determining an NH3 concentration in exhaust gases from an engine are provided. In one exemplary embodiment, a method includes generating a first signal from an NH3 sensor fluidly communicating with the exhaust gases. The method further includes generating a second signal from an air humidity sensor disposed proximate to an air intake manifold of the engine indicating a humidity level. The method further includes determining an air/fuel ratio associated with the engine. The method further includes determining an NH3 deviation value in a calibration table based on the second signal and the air/fuel ratio, utilizing a controller. The method further includes determining an NH3 concentration value based on the first signal and the NH3 deviation value, utilizing the controller. The NH3 concentration value is indicative of the NH3 concentration in the exhaust gases. The method further includes storing the NH3 concentration value in a memory device, utilizing the controller.

Abstract: The control apparatus for the internal combustion engine includes: a unit for detecting the change in the alcohol concentration of a fuel supplied to the internal combustion engine including a plurality of cylinders; a unit for detecting an air-fuel ratio variation between the plurality of cylinders; a unit for making the failure diagnosis when the air-fuel ratio variation between the plurality of cylinders exceeds a predetermined threshold value; and a unit for inhibiting the failure diagnosis executed based on the air-fuel ratio variation between the plurality of cylinders when the change in the alcohol concentration is detected.

Abstract: A gas concentration measuring apparatus for use in air-fuel ratio control of motor vehicle engines is provided which is designed to detect and identify a cause of failure in operation of an A/F sensor. The apparatus works to apply the voltage to a sensor element and sweep it to produce a change in electrical current flowing through the sensor element for measuring the impedance of the sensor element. The apparatus samples values of the change in the current, a sensor output indicating an air-fuel ratio of mixture supplied to the engine, etc., before and/or after the sensor element is activated and uses a combination thereof to identify the cause of the failure of the A/F sensor.

Abstract: An installation structure for a gas sensor capable of detecting gas concentration in a highly accurate manner is provided. The installation structure for a gas sensor which detects concentration of gas circulating inside an outlet-side piping comprises a through hole 18 in an inner wall of the outlet-side piping and the gas sensor comprises a gas inlet portion with one face open within the outlet-side piping 14, and the gas sensor is installed to the outlet-side piping in a condition where the gas inlet portion does not protrude from the inner wall of outlet-side piping.

Abstract: A method for determining an air ratio in a burner for a fuel cell heater having an ionization sensor in the range of the flame and which is fed with two different gases for combustion, one of said gases being obtained from a gas treatment, wherein a measurement signal of the ionization sensor is converted into an actual value for the air ratio depending on one or more variable of states of the gas treatment.

Abstract: A process for manufacturing a gas sensor, the gas sensor including a gas detecting element, cylindrical metal shell, and cylindrical protector as defined herein, the process comprising: applying a lubricant to an outer circumference of a leading end portion of the metal shell; assembling the metal shell having the lubricant applied thereto and the protector, so that a fitting portion, in which the leading end portion of the metal shell and the protector fit on each other, and a space-forming portion, in which the leading end portion of the metal shell and the protector overlap each other through an annular space, are formed along an axial direction; and welding the metal shell and the protector by forming a welded portion extending from an outer circumference of the protector through the annular space.

Abstract: A method of treating a gas sensor element for improving measurement characteristics thereof, including: heating the gas sensor element at a temperature of 600-1000° C. for 3-24 hours in a treatment atmosphere in which an oxygen concentration is regulated to be not higher than 0.2% and in which are included: (A) not lower than 1000 ppm of an adsorptive gas component wherein an adsorptive capable of being adsorbed on the measuring electrode is bound to oxygen; and (B) a combustible gas in an amount that can be substantially stoichiometrically oxidized by oxygen that is generated upon reduction or decomposition of the adsorptive gas component, so that the adsorptive gas component is reduced or decomposed for permitting the adsorptive in the adsorptive gas component to be adsorbed on the measuring electrode, and so that the noble metal material of the measuring electrode is reduced.

Abstract: An oxygen sensor 10 includes an oxygen detection element 20, which assumes a hollow tubular shape extending along the axis. The oxygen detection element 20 has a closed tip end and an opened rear end. An internal electrode layer 23 is formed on an inner circumferential surface 22 of the oxygen detection element 20. The sensor 10 also has a terminal member 30 which is in contact with the internal electrode layer 23 and in electrical connection therewith. The terminal member 30 has press contact portions 34c and 34d which come into press contact with the inner circumferential surface 22 of the oxygen detection element 20 to hold the terminal member 30 in the oxygen detection element 20, and conduction portions 35b which come into press contact with the internal electrode layer 23 on the inner circumferential surface 22 of the oxygen detection element 20 and into electrical connection with the internal electrode layer 23.

Abstract: In a compression ignition internal combustion engine provided with an NOx storage-reduction catalyst on an exhaust system, when the air fuel ratio of the exhaust gas being in a lean state is controlled to a rich state, a response time (ResS) from a time point an air fuel ratio sensor detects a first air fuel ratio (AF1), which is leaner than a stoichiometric air fuel ratio (AFS), to a time point the air fuel ratio sensor detects a second air fuel ratio (AF2), which is equal to or leaner than the stoichiometric air fuel ratio (AFS) and richer than the first air fuel ratio (AF1). When the response time (ResS) exceeds a stoichiometric air fuel ratio shift reference time (StdS), a determination is made that the air fuel ratio sensor is degraded.

Abstract: A gas sensor apparatus 3 in an air-fuel ratio detection system 1 includes a gas sensor element 4 which outputs a detection signal corresponding to air-fuel ratio, and a gas sensor control circuit 2 which includes a detection section 20 for outputting a first output signal VIP1, a second output signal VIP2, and a third output signal VIP3 in accordance with the detection signal. This detection section 20 outputs the first output signal VIP1 which changes in accordance with the air-fuel ratio at least within a wide first air-fuel ratio zone, the second output signal VIP2 which changes in accordance with the air-fuel ratio within a narrow zone in the vicinity of the stoichiometric ratio, and the third output signal VIP3 which changes in accordance with the air-fuel ratio within a narrow zone in the lean region.

Abstract: A gas sensor element which may be employed in measuring the concentration of gas such O2 is provided. The gas sensor element is of a laminated type and designed to introduce gas to be measured into a measurement gas chamber through a diffusion resistor. The measurement gas chamber has a volume of 0.15 mm3 in order to facilitate expelling of the gas remaining within the measurement gas chamber during transition of thermal activation of the gas sensor element.

Abstract: The degradation simulator is used for a gas sensor including a sensor element having a solid electrolyte layer and a pair of electrodes located opposite to each other across from the solid electrolyte layer, the sensor element outputting a sensor output signal having a value depending on concentration of a specific gas in the ambient gas. The degradation simulator includes a first setting function of enabling variably setting a time constant delay which appears on the sensor output signal when concentration of the specific gas changes, a second setting function of enabling variably setting a dead time delay which appears on the sensor output signal when concentration of the specific gas changes, and an adding function of adding at least one of the time constant delay and dead time delay to the sensor output signal in order to generate a pseudo-degraded sensor output signal in accordance with an external instruction.

Abstract: A gas sensor having an elastic insulating member including a longitudinal hole for receiving an air permeability filter assembly and a passage portion communications between the longitudinal hole and an outer side thereof.

Abstract: A gas sensor control unit (1) including a single signal-switching and outputting circuit (33) adapted for switching and outputting plural signals transmitted from plural gas sensors (8,9).

Abstract: A gas concentration measuring apparatus for use in air-fuel ratio control of motor vehicle engines is provided which includes a laminated sensor element and a sensor circuit. The sensor circuit includes a current-measuring resistor, at least one amplifier, and A/D converters. The current-measuring resistor functions to measure a current signal flowing through the sensor element produced upon application of the voltage to the sensor element. The amplifier works to amplify the current signal to output it to one of the A/D converters to determine the concentration of the air-fuel ratio within one of a plurality of measurement ranges defined within the wide gas concentration measuring range. The amplification of the current signal results in expansion of the level of the input to the A/D converter, thus enhancing the resolution in determining the air-fuel ratio.

Abstract: A system for determining a temperature of exhaust gases from an engine is provided. The system includes an exhaust gas sensor having an electric heating coil. The sensor communicates with exhaust gases from the engine. The system further includes an electrical circuit for generating a signal indicative of the resistance of the heating coil when the coil is not energized. Finally, the system includes a controller receiving the signal and calculating the temperature of the exhaust gases based on the signal.

Abstract: A method of monitoring a performance of an oxygen sensor is disclosed. One embodiment comprises determining a first air/fuel ratio from a signal from an exhaust oxygen sensor; determining a second air/fuel ratio from a temperature upstream of the particulate filter, a pressure differential across the particulate filter and one or more of an airflow into the engine and a fuel flow into the engine; comparing the first air/fuel ratio and the second air/fuel ratio; and diagnosing an error condition of the oxygen sensor if the first air/fuel ratio does not meet a predetermined condition relative to the second air/fuel ratio.

Abstract: A linear exhaust-gas probe has a measuring cell for measuring a gas concentration in a measuring chamber by determining a measuring-cell voltage, and a pump cell for pumping gas by way of a pump current. A circuit configuration for operating the prove has a comparator circuit for comparing the measuring-cell voltage with a measuring-cell setpoint voltage and for providing a corresponding analog deviation signal. A pump current source provides the pump current. The source is controlled by the deviation signal using a control circuit for the approximation of the measuring cell voltage to the measuring cell setpoint voltage. In order to reliably limit the pump voltage with no significant detrimental effect on the operation, the circuit configuration further has a second comparator circuit for comparing the pump voltage with a predefined threshold voltage and for providing a corresponding binary switching signal; and a counter coupling path between the output of the pump current source and the control circuit.

Abstract: In a gas sensor, a seal member is filled in an annular space disposed between abutted inward and outward shoulder portions of a housing and a sensor member and an one open end of the housing. A tubular insulator is installed in the annular space to be mounted at its first end surface on the seal member. A ring member is installed in the annular space to be mounted at its first end surface on a second end surface of the tubular insulator. The one open end of the housing is configured to be inwardly crimped such that an edge of an inner circumference of the inwardly crimped one open end of the housing digs in a second end surface of the ring member to thereby fixedly press the seal member, the insulator, and the ring member to the abutted inward and outward shoulder portions.

Abstract: The present invention provides a sensor capable of maintaining an electrical connection between the lead frame and an electrode terminal section of the detection element even when an inadequate external force is applied to a lead frame and a sensor production method capable of preventing the lead frame from buckling and being deformed into an inadequate shape. The lead frame (second lead frame) can inhibit movement of a second frame main body section axially toward a rear end side through engagement of a third locking surface of a second locking section with a second locking groove and can inhibit the second frame main body section from going apart from an inner surface of an insertion hole through engagement of a fourth locking surface of the second frame locking section, which faces an element engagement section side.

Abstract: An exhaust gas analyzer includes a main flow path and at least one sub-flow path. Exhaust gas from an internal combustion engine is introduced to the main flow path; sub-flow paths are parallel to the main flow path. Plural kinds of analyzers are mounted on the main flow path and sub-flow paths to measure concentration of multiple components in the exhaust gas. Actual measurement values of the concentration for the measured components are obtained. A deviance from a true value generated to an actual measurement value due to a mutual influence of the measured components is corrected based on at least one actual measurement value.

Abstract: An oxygen sensor for measuring exhaust gases of an internal combustion engine is described. The sensor provides an output that has a high gain near the stoichiometric air-fuel ratio, and a lower gain in the lean and rich air-fuel ratio regions. Further, the sensor provides wide range air-fuel ratio signal to be used in engine feedback control.

Abstract: A gas sensor for detecting at least one physical magnitude of a gas, in particular of exhaust gases of an internal combustion engine, is proposed, which includes a sensor element having an electrochemical cell. The electrochemical cell includes a first solid electrolyte member on which a first electrode and a second electrode are applied. The first and the second electrode are electrically connected by means of the first solid electrolyte member. The first electrode is in contact with the gas. The area of the first electrode is smaller than the area of the second electrode.

Abstract: In a gas concentration detecting apparatus, a voltage is applied to electrodes of a sensor element. A change is caused in either the applied voltage or an element current. An amount of a change in each of a current value and a voltage value caused is measured in response to the caused change. An amount of resistance of the sensor element is calculated based on a ratio between the change amounts in the current value and the voltage value. A detection unit detects abnormality relating to controlling the sensor by utilizing at least one of the change amounts in the current value and the voltage value.

Abstract: An SOF measuring system that can continuously measure SOF and a soot measuring system that can continuously measure soot are connected with an exhaust gas line. The soot measuring system comprises a diluter that selectively dilutes either one of the exhaust gas and standard gas whose hydrocarbon concentration is known with diluent gas and extrudes it. A dilution ratio adjusting device can adjust a dilution ratio of the diluter. A soot detector continuously detects soot in the exhaust gas or the standard gas diluted by the diluter. The SOF measuring system can be connected with the diluter so that an exhaust gas analyzer can measure the hydrocarbon concentration in the standard gas diluted by the diluter.

Abstract: An oxygen concentration detection system including an oxygen sensor which outputs a plurality of types of measurement signals and anomaly detection means and modification means. The anomaly detection means detects a sensor anomaly by determining whether the respective levels of the plurality of types of measurement signals fall within predetermined ranges. When a sensor anomaly is not detected, the modification means outputs the plurality of types of measurement signals as is. When a sensor anomaly is detected, the modification means outputs at least one of the plurality of types of measurement signals at a level outside the corresponding range within which the level of the measurement signal varies in a normal state.

Abstract: Respective positive terminal electric potentials of exhaust gas sensors are sequentially selectively inputted to an analog input terminal of a multi-channel AD converter through a multiplexer. An offset voltage is applied to respective negative terminals of the exhaust gas sensors. This offset voltage is inputted to another input terminal of the multi-channel AD converter. A microprocessor detects a generating voltage of the exhaust gas sensors by the difference between a digital converting value of the positive terminal electric potential and a digital converting value of the negative terminal electric potential. The microprocessor also individually judges that each of the digital converting values is excessively small and excessively large. Thus, the microprocessor judges the existence of ground, sky short circuit and disconnection abnormalities of the negative terminal and the positive terminal.

Abstract: An ECU controls an A/F sensor that is provided in an exhaust system of an internal combustion engine and produces current outputs corresponding to the concentration of oxygen in exhaust gas by being supplied with voltage and produces voltage outputs corresponding to the concentration of oxygen in exhaust gas according to the difference between the oxygen concentration around one of a pair of electrodes of the A/F sensor and the oxygen concentration around the other electrode. The ECU has: an energization limitation portion that, when moisture content is adhering on an inner face of an exhaust passage near the A/F sensor, energizes a heater of the A/F sensor while limiting the amount of power supplied thereto; and a specific output obtaining portion that obtains voltage outputs from the A/F sensor at least when the energization limitation portion is energizing the heater while limiting the amount of power supplied thereto.

Abstract: A gas sensor is described for detecting a physical property of a measuring gas, including detecting the oxygen concentration in the measuring gas. The gas sensor includes a sensor element having a diffusion barrier, which is arranged between a first solid electrolyte layer and a second solid electrolyte layer. The diffusion barrier has a necked-down portion, i.e., a concave profile, between the first and the second solid electrolyte layer. Accordingly, a first area, which the diffusion barrier occupies in a plane which lies between the side of the first solid electrolyte layer (facing the diffusion barrier) and the side of the second solid electrolyte layer (facing the diffusion barrier), is smaller than a second area on which the diffusion barrier covers the first or the second solid electrolyte.

Abstract: In an abnormality diagnostic device and an abnormality diagnostic device for an air-fuel ratio sensor that detects the air-fuel ratio of exhaust gas of an internal combustion engine, a system extending from a fuel injection valve to the air-fuel ratio sensor is model by a first order response delay, and a parameter in the first order response delay is identified based on an input air-fuel ratio that is given to the air-fuel ratio sensor and an output air-fuel ratio that is output from the air-fuel ratio sensor. Then, the presence/absence of abnormality regarding a predetermined characteristic of the air-fuel ratio sensor is determined based on the parameter identified. Thus, abnormality is diagnosed regarding individual characteristics of the air-fuel ratio sensor.

Abstract: A diagnosis device calculates a lean-direction responsiveness characteristic and a rich-direction responsiveness characteristic of the exhaust gas sensor. The lean-direction responsiveness represents a responsiveness of the sensor in a case that an air-fuel ratio is controlled in such a manner as to be varied in a lean direction. The rich-direction responsiveness represents a responsiveness of the sensor in a case that the air-fuel ratio is controlled in such a manner as to be varied in a rich direction. The diagnosis device determines whether the exhaust gas sensor deteriorates based on at least one of the lean-direction responsiveness characteristic and the rich-direction responsiveness characteristic, and on a comparison result between the lean-direction responsiveness characteristic and the rich-direction responsiveness characteristic.

Abstract: In a method for checking the lambda value ? indicated by a binary lambda probe, the lambda probe being situated in the exhaust line of an internal combustion engine and provided downstream from a catalyst having oxygen storage capacity, the invention provides that the time progression of the voltage signal U? is plotted in the range of the lambda value ?actual of 1.0 indicated by the lambda probe until a first inflection point W1 and a second inflection point W2 of the voltage signal U? have been detected, the time derivative dU?/dt of the voltage signal is generated, the jumps S1, S2 in the time derivative dU?/dt which occur at the inflection points W1, W2 are compared to one another, and based on the comparison of the jumps S1, S2 the indicated lambda value ?actual of 1.0 is checked. According to the invention, the actual lambda value ?target of 1.

Abstract: A cylinder deviation of an actual air-fuel ratio before an air-fuel-ratio dither control is obtained based on a variation of an actual air-fuel ratio by the dither control, a variation amount of detected air-fuel ratio, and a cylinder deviation of detected air-fuel ratio before the dither control A cylinder deviation of actual air-fuel ratio of each cylinder is accurately estimated. When the number of times in which the cylinder deviation of air-fuel ratio exceeds a decision value is greater than a predetermined number, it is determined that an abnormality occurs in the cylinder.

Abstract: The invention is distinguished by a method and a corresponding device for diagnosis of an individual catalytic converter of an exhaust gas purification unit assigned to an internal combustion engine in the Y configuration, despite the lack of exhaust gas probe between the individual catalytic converter and a main catalytic converter. The diagnosis proceeds on the basis of signals from the exhaust gas probes belonging to the exhaust gas purification unit. On the basis of these signals, the oxygen storage capacity of the individual catalytic converter is determined despite the lack of exhaust gas probe between the individual catalytic converter and the main catalytic converter.

Abstract: A gas concentration detection apparatus includes a series-connected combination of a sensor element and a resistor, with an AC voltage being applied to one of the outer terminals of that combination and with the other outer terminal being held at a fixed potential. A DC voltage signal at a level determined by an oxygen concentration that is detected by the sensor element, and an AC voltage signal at an amplitude determined by sensor element impedance and hence by the sensor element activation status, are extracted from the series-connected combination by respectively separate circuits which apply separately determined amplification factors.