| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a degradation diagnostic device for an A/F sensor 26 diagnosing the degradation of the A/F sensor 26 with higher accuracy. Ž<P>SOLUTION: When an air-fuel ratio detected by the A/F sensor 26 is feedback controlled to a target value, firstly, the minimum value of the output of the A/F sensor 26 is detected. Then, it is determined whether or not the absolute value of a difference between the minimum value of the output of the A/F sensor 26 and the output value of the A/F sensor 26 when a predetermined period elapses from a point of time with the output of the A/F sensor becoming the minimum value is equal to or less than a threshold β. When it is determined that the absolute value is equal to or less than the threshold β, it is diagnosed that the A/F sensor 26 is degraded. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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