| 摘要 |
<p>PURPOSE:To enable any trouble to be decided certainly, in the device in which a control valve is interposed in the secondary air introducing passage opening to an exhaust gas passage on the upper course from an oxygen sensor by providing such a constitution that the trouble condition of the control valve is decided from outputs from the oxygen sensor at the time of opening and closing of the control valve. CONSTITUTION:A secondary air introducing passage 3 is opened at the position of an exhaust gas passage 2 on the upper course side from the setting position of an oxygen sensor 1 for detecting oxygen concentration in exhaust gas, and a control valve 5 is interposed on the way of the introducing passage 3. This control valve 5 is controlled by a controlling circuit 4 to close at the time of a low/high load or the like as well as to open at the time of a preset operation such as with a partial load or the like. In a secondary air introducing device such as this one a trouble diagnosing means 6 is provided for judging the trouble condition of the control valve 5 from outputs of the oxygen sensor 1 at the time of opening/closing valve of the control valve 5. Oxygen sensor output at the time of opening the control valve 5 is compared with oxygen sensor output at the time of closing the valve, so that the trouble of the control valve 5 is decided, when the difference is less than a prescribed value.</p> |
