| 摘要 |
PROBLEM TO BE SOLVED: To discover a failure of an air-fuel ratio sensor at an early stage by forcedly performing air-fuel ratio feed back control when the air-fuel ratio sensor fails from start of an engine for shortening period of a state that exhaust gas noxious component increases. SOLUTION: In a failure diagnosis device for the air-fuel ratio sensor provided with the air-fuel ratio sensor detecting oxygen concentration in exhaust gas in an exhaust gas passage of the engine and provided with an air-fuel ratio feedback control means performing air-fuel ratio feedback control with using the air-fuel ratio sensor, a determination means determining a failure of the air-fuel ratio sensor if output voltage of the air-fuel ratio sensor never exceeds rich lean determination voltage after predetermined time passes from start of air-fuel ratio feedback control is provided. COPYRIGHT: (C)2006,JPO&NCIPI
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