| 摘要 |
PURPOSE:To utilize an existent device effectively and to detect a decrease in the function of the catalyst converter by comparing the ratio of the outputs of O2 sensors provided on the upstream and downstream sides of the catalyst converter with a specific comparison decision value. CONSTITUTION:A control program is stored in an electronic controller (microcomputer unit) 6. The ratio obtained by dividing the output voltage X1-alpha of the O2 sensor 2 provided on the upstream side of the catalyst converter 1 by the output voltage Y1 of the O2 sensor 3 on the downstream side is determined. The deterioration state of the converter 1 is decided according to the value calculated by subtracting 1 from the ratio. Here, the voltage Yi is the latest value and the voltage X1-alpha is a value which is a specific time of alpha seconds precedent. The alpha seconds are a variable corresponding to the flow velocity of exhaust gas while based upon a parameter of the amount of sucked air or injected fuel, etc. Under those set conditions, the mean value of several values is determined and it is decided that the converter 1 deteriorates and is abnormal when the value is nearly equal to the comparison decision value, e.g. 0. The result is displayed by the illumination of, for example, a diagnostic lamp. |
