| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a secondary air supply system capable of diagnosing existence of unusual condition of a control valve in a short time without giving influence to exhaust emission nor causing deterioration of parts. <P>SOLUTION: A first control valve 21 and second control valves 22a and 22b are arranged downstream of an air pump 10, and a pressure sensor 20 is arranged between the air pump and the first control valve. In the condition that the first control valve and the second control valves are closed, the air pump is operated to accumulate air between the air pump and the first control valve, and thereafter, the first control valve is opened. At that time, existence of unusual condition of the first control valve is diagnosed on the basis of fluctuation of the pressure between the air pump and the first control valve detected by a pressure detecting means. When fluctuation more than the predetermined width is detected, diagnosis that the first control valve is in the usual condition is done, and when fluctuation is not detected, diagnosis that the first control valve is in the unusual condition is done. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
