Mitsubishi Jidosha Kogyo Kabushiki Kaisha

Kazumichi Takahashi

Yuji Sato

Hideo Matsunaga

Katsuhiro Furuta

Junya Kitada

A deterioration determination unit determines whether a catalyst in an exhaust passage of an engine is deteriorated; a first determination unit determines whether there is an air-fuel ratio variation among cylinders of the engine on the basis of distortion in waveform of the air-fuel ratio on the upstream side of the catalyst; and a second determination unit determines whether there is an air-fuel ratio variation among the cylinders on the basis that the air-fuel ratio on the downstream side of the catalyst remains on the lean side. A determination mode switching unit makes the first determination unit execute a determination process concurrently with determination by the deterioration determination unit, and it is determined by the determination process that there is an air-fuel ratio variation among the cylinders, makes the second determination unit execute a determination process in priority to determination of deterioration of the catalyst.

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Obu, Japan

Kazumichi Takahashi