Abstract: To provide a malfunction diagnosing method and apparatus capable of reliably determining a malfunction even where the malfunction occurs in a common wire connecting a gas sensor and a control circuit for driving it. In a gas concentration measurement unit 1 having a sensor control circuit 50 which is connected to a sensor element 10 including an oxygen pump cell 14 and an oxygen concentration detection cell 24 and controls and drives this sensor element 10, a variation state of a terminal voltage at one connecting point (specifically, a Vs+ terminal) other than connecting points between electrodes facing a measurement chamber of each cell 14 and 24 and a common wire 24 is detected by a malfunction detection circuit 53 and an arithmetic processor 54. Based on this variation state of the terminal voltage, diagnosis of malfunction in the common wire 42 is executed. When the common wire 42 is broken, the terminal voltage at the Vs+ terminal varies with oscillations.

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 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: A gas sensor diagnostic method includes: a fuel supply detecting step of detecting an interruption of a fuel supply to the internal combustion engine, and a restart of the fuel supply after the interruption of the fuel supply; a response time period accumulating step of determining a response time period by accumulating a first time period that the sensor output value reaches from a first threshold value to a second threshold value after the detection of the interruption of the fuel supply, and a second time period that the sensor output value reaches from a third threshold value to a fourth threshold value after the detection of the restart of the fuel supply after the interruption of the fuel supply; and an abnormal state diagnosing section of determining an abnormal state of the gas sensor when the response time period is greater than a predetermined time period.

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 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 first moderated signal by applying a first moderation calculation to the detection signal, and a second moderated signal by applying a second moderation calculation to the detection signal; calculating a deviation between the first and second moderated signals; and determining whether the gas sensor is in the abnormal state on the basis of the deviation obtained during the diagnosis period.

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 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 first moderated signal by applying a first moderation calculation to the detection signal, and a second moderated signal by applying a second moderation calculation to the detection signal; calculating a deviation between the first and second moderated signals; and determining whether the gas sensor is in the abnormal state on the basis of the deviation obtained during the diagnosis period.

Abstract: A gas sensor diagnostic method includes: a fuel supply detecting step of detecting an interruption of a fuel supply to the internal combustion engine, and a restart of the fuel supply after the interruption of the fuel supply; a response time period accumulating step of determining a response time period by accumulating a first time period that the sensor output value reaches from a first threshold value to a second threshold value after the detection of the interruption of the fuel supply, and a second time period that the sensor output value reaches from a third threshold value to a fourth threshold value after the detection of the restart of the fuel supply after the interruption of the fuel supply; and an abnormal state diagnosing section of determining an abnormal state of the gas sensor when the response time period is greater than a predetermined time period.

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 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: To provide a malfunction diagnosing method and apparatus capable of reliably determining a malfunction even where the malfunction occurs in a common wire connecting a gas sensor and a control circuit for driving it. In a gas concentration measurement unit 1 having a sensor control circuit 50 which is connected to a sensor element 10 including an oxygen pump cell 14 and an oxygen concentration detection cell 24 and controls and drives this sensor element 10, a variation state of a terminal voltage at one connecting point (specifically, a Vs+ terminal) other than connecting points between electrodes facing a measurement chamber of each cell 14 and 24 and a common wire 24 is detected by a malfunction detection circuit 53 and an arithmetic processor 54. Based on this variation state of the terminal voltage, diagnosis of malfunction in the common wire 42 is executed. When the common wire 42 is broken, the terminal voltage at the Vs+ terminal varies with oscillations.