| 摘要 |
PROBLEM TO BE SOLVED: To provide an oxygen sensor diagnosis device for an internal combustion engine having high diagnosing accuracy and reliability without an error in determining that an oxygen sensor on the downstream side of a catalyst is malfunctioned although it is normally functioned. SOLUTION: The device comprises a means for calculating the amount of O2 supplied to the catalyst or desorbed from the catalyst in accordance with an engine intake air amount and an air-fuel ratio on the upstream side of the catalyst, a means for calculating the storage amount of O2 in the catalyst from a cumulative value for the amount of O2, a malfunction determining means for determining that the oxygen sensor on the downstream side of the catalyst in accordance with the output of the oxygen sensor on the downstream side of the catalyst during a period from fuel cut to fuel cut recovery, a means for setting a predetermined time equivalent to a time required for supplying air to the catalyst when starting fuel cut, and a storage means for storing the storage amount of O2 in the catalyst at the time when the predetermined time passes after starting fuel cut. When the storage amount of O2 in the catalyst stored in the storage means is a predetermined value or greater in Step 1003, determination is not made in Step 506 that the oxygen sensor on the downstream side of the catalyst is malfunctioned. COPYRIGHT: (C)2008,JPO&INPIT
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