| 摘要 |
An apparatus for detecting deterioration of a catalyst in an internal combustion engine initially biases an air/fuel ratio of an air-fuel mixture supplied to the internal combustion engine to a rich amount so that an amount of oxygen stored in the catalyst is substantially zero. Then, the apparatus detects deterioration of the catalyst by alternating the air/fuel ratio lean or rich based on an amount of oxygen given to the catalyst. If the catalyst has deteriorated, a bias amount of the air/fuel ratio is set so that the amount of oxygen stored in the catalyst is substantially saturated. If the catalyst is normal, a bias amount of the air/fuel ratio is set so that the amount of oxygen stored in the catalyst is not saturated.
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