摘要 |
A main feedback control based on an output of an upstream sensor, and a sub-feedback control based on an output of a downstream sensor are executed. A specified fuel disturbance is inputted and an output of the downstream sensor is measured to derive a characteristic value. Based on the characteristic value, it is determined whether a purifying capacity of the exhaust gas purifying system including the catalyst, the upstream sensor, and the downstream sensor is deteriorated.
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