| 摘要 |
<p>PURPOSE:To prevent erroneous judgment by diagnosing an exhaust gas purifying device while taking both deterioration of catalyst and that of a catalyst front sensor, into consideration. CONSTITUTION:Degree of deterioration of a catalyst 1 is estimated by utilizing an output signal of a catalyst rear sensor 3. Additionally, deterioration judgment level which must be satisfied at least by the catalyst front sensor 2 is determined based on the estimated deterioration degree, and it is judged whether the deterioration judgment level is satisfied or not by the catalyst front sensor 2. When it is satisfied, deterioration of the catalyst is diagnosed by utilizing the output signals of the catalyst front sensor and the catalyst rear sensor.</p> |
