| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an abnormality determination device for an oxygen sensor provided downstream of a catalyst and determining the abnormality of the oxygen sensor, suppressing erroneous determination caused by such an event that the output value of the oxygen sensor is gradually changed to a lean side before a fresh air reaches the oxygen sensor downstream of the catalyst, and enabling efficient abnormality determination with the improved accuracy of determination on whether the event occurs or not. Ž<P>SOLUTION: A first determination means acquires the lowered amount of the output value of the oxygen sensor during a period from an idle-on time to the start of fuel cut, and determines whether the lowered amount of the output value is smaller than a preset reference lowered amount or not (ST2-ST5). A second determination means determines whether a response time required for the output value of the oxygen sensor to be changed from a first reference value to a second reference value is longer than a preset reference response time or not after the fuel cut is started (ST8-ST14). When positive determination is made by the first determination means and positive determination is made by the second determination means, the oxygen sensor is determined to be abnormal (ST18). Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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