| 摘要 |
An abnormality determination apparatus for an oxygen sensor provided on the downstream side of a catalyst includes: a first determination portion that determines whether a rich-output continuation time during which output value of the oxygen sensor continues being an output value that shows a rich state before a fuel cut is started is longer than a set continuation time; a second determination portion that determines whether degree of change in the output value when the output value changes from a first reference value to a second reference value that shows a leaner state than the first reference value is more gradual than a set degree of change after the fuel cut is started; and a third determination portion that determines whether the oxygen sensor is abnormal based on determinations by the first determination portion the second determination portion.
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