| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a failure diagnosis device of an oxygen sensor capable of improving diagnosis accuracy by preventing erroneous determination. <P>SOLUTION: This failure diagnosis device of the oxygen sensor provided in an exhaust passage of an internal combustion engine is equipped with an output voltage detection means for detecting an output voltage of the oxygen sensor 19; an exhaust gas quantity estimation means for estimating an exhaust gas quantity in a reference gas chamber of the oxygen sensor; a failure diagnosis execution permission period setting means for setting a permission period during which execution of failure diagnosis of the oxygen sensor is permitted, when the exhaust gas quantity estimated by the exhaust gas quantity estimation means reaches the first prescribed value and exceeds the second prescribed value smaller than it; and a failure determination means for determining that the oxygen sensor is failed, when a negative output value is detected by an output voltage detection means after a lean air-fuel ratio operation state over a prescribed value is continued as long as a prescribed time, in the failure diagnosis execution permission period set by the failure diagnosis execution permission period setting means. <P>COPYRIGHT: (C)2009,JPO&INPIT |
