| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent an erroneous diagnosis due to an effect of sulfur in fuel. <P>SOLUTION: A catalyst deterioration diagnostic system includes a means 20 for stoichiometrically controlling the air-fuel ratio based on output of at least a pre-catalyst air-fuel ration sensor 17 by making a feedback process, a means 20 for measuring oxygen storage capacity of a catalyst 11, and a means 20 for correcting an oxygen storage capacity measured value based on output behavior of a post-catalyst air-fuel ratio sensor 18 in at least stoichiometric feedback control. The oxygen storage capacity measured value is corrected by using the fact that post-catalyst air-fuel ratio sensor output behavior in the stoichiometric feedback control is different in response to the sulfur concentration of the fuel. The measured value is corrected to a value corresponding to low sulfur using time, and a diagnosis is performed after removing the sulfur effect, thereby the erroneous diagnosis can be prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT |
