Patent ID: 7248960

Claim:
An air-fuel ratio sensor failure detecting apparatus designed to detect a predetermined failure of an air-fuel ratio sensor installed in an exhaust line of an internal combustion engine, comprising: a correction factor determining circuit working to determine an air-fuel ratio correction factor to bring an air-fuel ratio, as detected through the air-fuel ratio sensor, into agreement with a target value; an air-fuel ratio change data determining circuit working to determine air-fuel ratio change data associated with changes in the detected air-fuel ratio to a rich and a lean side, respectively; an air-fuel ratio correction factor change data determining circuit working to determine air-fuel ratio correction factor change data associated with changes in the air-fuel ratio correction factor upon changes in the air-fuel ratio to the rich and lean sides, respectively; a response characteristic determining circuit working to determine response characteristics of the air-fuel ratio sensor upon the changes in the air-fuel ratio to the rich and lean sides, respectively, as functions of the air-fuel ratio change data and the air-fuel ratio correction factor change data; and a sensor failure detecting circuit working to detect the predetermined failure of the air-fuel ratio sensor based on the response characteristics, as determined by said response characteristic determining circuit.