| 摘要 |
<p>PURPOSE:To provide a catalyst deterioration determination device which is rarely affected by the dispersion and deterioration of unitary performance of an O2 sensor. CONSTITUTION:Ordinarily, a first air fuel ratio control means M1 feed-back- controls an air fuel ratio based on the output of both an upstream side O2 sensor FS and a downstream side O2 sensor RS for a catalyst C. When an operation state determination means M3 identifies a specified engine operation state, an adjustment means switch means M4 switches from a first air fuel ratio adjustment means M1 to a second air fuel ratio adjustment means M2 and feed-back-controls the air fuel ratio based on only the output of the downstream side O2 sensor RS. At this time, a time measuring means M6 measures the length of time between the point of time when the amount of skip which causes the increase of the air fuel ratio occurs and the point of time when a reverse determination means M5 detects the reversal of the output of the downstream side O2 sensor RS and when the length of time becomes shorter than a specified value, a catalyst deterioration determination means M7 determines that the catalyst C is deteriorated.</p> |
