| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve the accuracy of diagnosis for degradation in an exhaust gas cleaning catalyst required for an internal combustion engine loaded on a vehicle. <P>SOLUTION: The diagnosis for estimating an oxygen occlusion capacity of the exhaust gas cleaning catalyst mounted on an exhaust passage of an internal combustion engine is performed by referring to the output of air-fuel ratio sensors respectively provided upstream and downstream with respect to the exhaust gas cleaning catalyst and estimating the oxygen amount occluded in the catalyst through the measurement of elapsed time from the time when output of the upstream side sensor varies to the time when output of the downstream side sensor varies. In the diagnosis, when the diagnosis is performed in an acceleration period, it is determined whether the catalyst is abnormal or not after the degradation determination threshold value is corrected lower as the degree of the acceleration is larger. <P>COPYRIGHT: (C)2012,JPO&INPIT |
