| 摘要 |
PROBLEM TO BE SOLVED: To provide an abnormality diagnosis system for a limit current type gas sensor for detecting oxygen-containing gas included in exhaust gas of an internal combustion engine.SOLUTION: In a gas sensor, a decomposition current value of water (HO) is detected S530, and based on a deviation S540, S550 from a reference decomposition current value S535 corresponding to a concentration of water included in exhaust gas, a diagnosis is made to determine whether or not output characteristics of the limit current type gas sensor have an abnormality S545, S555. This diagnosis enables not only a significant abnormality of the output characteristics but also a minute abnormality to be determined accurately and easily. The water reference decomposition current value can be acquired based on a water concentration detected by a separate humidity sensor or a decomposition current value of oxygen detected by the limit current type gas sensor. In the latter case, the acquired water reference decomposition current value may be corrected based on the decomposition current value of oxygen detected during fuel cut.SELECTED DRAWING: Figure 5 |
