| 摘要 |
PROBLEM TO BE SOLVED: To obtain an apparatus for diagnosing abnormality of an air/fuel ratio sensor, capable of accurately diagnosing abnormality of the air/fuel ratio sensor, in a short time. SOLUTION: When it is detected that the supply of fuel is stopped (S16), the change quantity DAF of an air/fuel ratio during a prescribed change quantity calculation periodΔT (e.g. 200-300 ms) is calculated successively, on the basis of the output of the air/fuel ratio sensor for detecting the air/fuel ratio of exhaust gas (S22, change quantity calculation means). A maximum value DAFMAX of a plurality of change quantities thus calculated is compared with a preset deciding standard value DAFSAF (S34), and when the maximum value is smaller than the deciding reference value, it is decided that there is abnormality (S46, judging means).
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