Patent ID: 7340945

Claim:
A failure detection apparatus for an exhaust gas sensor that has an exhaust-side electrode exposed in an exhaust passage of an internal combustion engine, an atmosphere layer forming member that forms an atmosphere layer in an interior of the exhaust passage, an atmosphere-side electrode exposed to the atmosphere layer, and an electrolyte layer that is disposed between the exhaust-side electrode and the atmosphere-side electrode and that allows movement of oxygen ions between the exhaust-side electrode and the atmosphere-side electrode, the failure detection apparatus comprising: a reverse voltage application device that applies a reverse voltage between the atmosphere-side electrode and the exhaust-side electrode so that an electric potential of the exhaust-side electrode becomes higher than an electric potential of the atmosphere-side electrode; a reverse current detection device that detects a value of reverse current that flows between the atmosphere-side electrode and the exhaust-side electrode in association with application of the reverse voltage; an impedance correlation value acquisition device that acquires an impedance correlation value that has a correlation with an impedance between the atmosphere-side electrode and the exhaust-side electrode; and a failure detection portion that detects a failure of the exhaust gas sensor by comparing the value of reverse current and a criterion value while taking into account an influence of the impedance superposed on the value of reverse current.