| 摘要 |
PURPOSE:To correctly judge the inactive state on the basis of the lean signal of the second air-fuel ratio sensor when the increased fuel state continues, in a catalytic converter equipped with the first and the second air-fuel ratio sensors for generating the signal in inactive state, on the upstream and downstream sides. CONSTITUTION:The first and the second air-fuel ratio sensors 13 and 15 for generating the lean signal in inactive state are installed onto the upstream and downstream sides of a catalytic converter 12. A control circuit 10 calculates the fundamental fuel feed quantity and the increased quantity in acceleration on the basis of each detection value of an air flow meter 3, crank angle sensors 5 and 6, and a throttle sensor 17, etc., and judges if the detection value of a downstream side O2 sensor 15 is in lean or rich side, when the increased fuel state continues for a prescribed time or more. When a downstream side O2 sensor 15 outputs the lean signal, trouble state is judged, and an alarm 18 is operated.
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