| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a diagnostic device for an exhaust emission control device capable of diagnosing the deterioration of a catalyst even if a responsive of an air-fuel ratio detection means at a catalyst downstream is deteriorated. <P>SOLUTION: A catalyst deterioration degree detection means 104 detects a deterioration degree of a catalyst from a relation between an air-fuel ratio detection means 101 at a catalyst upstream and the air-fuel ratio detection means 102 at a catalyst downstream. A catalyst deterioration degree correction means 111 corrects the deterioration degree of the catalyst detected by the catalyst deterioration degree detection means 104 from a drop response ratio which is a ratio of a drop response index of the air-fuel ratio detection means at the catalyst upstream and a drop response index of the air-fuel ratio detection means at the catalyst downstream, or a rise response ratio which is a ratio of a rise response index of the air-fuel ratio detection means at the catalyst upstream and rise response index of the air-fuel ratio detection means at the catalyst downstream. A catalyst deterioration determination means 112 determines the deterioration state of the catalyst from the information of a catalyst deterioration degree correction means 111. Consequently, the deterioration of the catalyst can be accurately determined even if the rise responsive of the air-fuel ratio sensor at the catalyst downstream is deteriorated. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
