| 摘要 |
PURPOSE:To improve fuel consumption and drivability, by a method wherein, in a device which has air-fuel ratio sensors located up and down a line from a catalyst converter, when activation of the O2 sensor on the downstream side is decided, feedback control of an air-fuel ratio by means of the O2 sensor on the downstream side is started rapidly. CONSTITUTION:First and second air-fuel ratio sensor means A and B, detecting concentration of a specified component in exhaust gas, are situated up and down a line from a catalyst converter mounted to the exhaust system of an engine. An output V1 from the first air-fuel ratio sensor means A is compared with a first given voltage VR1 by means of a first comparing means C. Depending upon whether an output V2 from the second air-fuel ratio sensor means B attains a second given voltage VR2, activation of the sensor means B is discriminated by means of a non-activation discriminating means D. During discrimination of activation, the output V2 is compared with a third given voltage VR2 by means of a second comparing means E. Based on outputs from the two comparing means C and E, the air-fuel ratio of an engine is regulated by an air-fuel ratio regulating means F.
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