| 摘要 |
PROBLEM TO BE SOLVED: To correct an output shift produced in an air-fuel ratio sensor installed upstream of a catalyst in an environment of a rich air-fuel ratio where hydrogen is easily generated.SOLUTION: An exhaust gas air-fuel ratio at an upstream side of a catalyst is controlled to a rich air-fuel ratio on a richer side than a theoretical air-fuel ratio. At detection timing when a reference time passes after an air-fuel ratio is specified as a rich air-fuel ratio, an output of a first sensor, which is an air-fuel ratio sensor installed at the upstream side of the catalyst on an exhaust path in an internal combustion engine, and an output of a second sensor, which is an air-fuel ratio sensor installed at a downstream side of the catalyst are detected. An output of the first sensor is corrected when the output of the first sensor indicates a value on a richer side than the theoretical air-fuel ratio according to a difference in the outputs between the first sensor and the second sensor. |
