| 摘要 |
PROBLEM TO BE SOLVED: To provide a trouble diagnostic device of a downstream side exhaust gas sensor capable of early detecting the trouble of the downstream side exhaust gas sensor when the operating state is changed from rich to lean and from lean to rich even in an internal combustion engine in which the number of times of rich operating state is small. SOLUTION: A control means comprises a diagnostic means measuring a response time in which the output value of the downstream side exhaust gas sensor changes between a lean determination value and a rich determination value and diagnosing the response state of the downstream side exhaust gas sensor by the response time. The diagnostic means has the function for stopping the measurement of the response time when the output value of the downstream side exhaust sensor is inverted while the response time is changed between the lean determination value and the rich determination value. COPYRIGHT: (C)2007,JPO&INPIT
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