| 摘要 |
PURPOSE:To prevent the erroneous control of air-fuel ratio by adjusting the air-fuel ratio according to the outputs of the air-fuel ratio sensors installed on the upstream and downstream sides of a catalytic converter, when the base air-fuel ratio is rich or the output of a pull-up type input circuit is less than a prescribed value, in the constitution in which the air-fuel ratio sensors are provided. CONSTITUTION:Air-fuel ratio sensors 13 and 15 are installed on the upstream and downstream sides of a three-component catalyst in an exhaust passage, and the output of the downstream side sensor 15 is inputted into a pull-up type input circuit 12. The first judging means MA judges if the output of the input circuit 12 is less than an activity judging level A or not, and if the judge ment is 'YES', the second judging circuit MB judges if the base air-fuel ratio is rich or less according to the variation rate of the output of the input circuit 12. After the judgement, if the third judging means MC judges that the output of the input circuit 12 is less than a prescribed value C, an air-fuel ratio adjusting means MD adjusts the air-fuel ratio according to the output of the downstream sensor 15, besides the output of the upstream sensor 13. |
