| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an abnormality diagnosis device for an oxygen sensor, for shortening a time required for determination of abnormality of the oxygen sensor to suppress degradation in emission, in abnormality diagnosis of the oxygen sensor which is disposed downstream a catalyst. <P>SOLUTION: An electronic control unit 22 forcibly changes an air-fuel ratio of the upstream of the catalyst 18 based on an air-fuel ratio of the downstream of the catalyst 18, and calculates an estimated oxygen occlusion of the catalyst 18 based on the air-fuel ratio of the downstream of the catalyst 18 which is changed at that time. Based on the comparison between the estimated oxygen occlusion and a determination value, whether or not there is any abnormality in the oxygen sensor 20 detecting the air-fuel ratio of the downstream of the catalyst 18 is diagnosed. In the diagnoses, the electronic control unit 22 updates the determination value for diagnosing whether or not there is any abnormality in the oxygen sensor 20 based on the estimated oxygen occlusion. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
