To provide a failure diagnosing device of an exhaust emission sensor, having high detection accuracy to a deterioration failure of the exhaust emission sensor and having a wider detection area.
This deterioration failure diagnosing device is provided for the exhaust emission sensor provided in an exhaust passage of an internal combustion engine to generate an output according to an exhaust emission component of the internal combustion engine. The device includes: a detection signal generating means for generating a detection signal by which a basic fuel injection quantity used in normal operation is multiplied to be taken as a fuel injection quantity for determining the state of the exhaust emission sensor; and an exhaust emission sensor evaluation means for extracting a frequency response to the detection signal from the output of the exhaust emission sensor of the internal combustion engine to the fuel injection quantity and determining the state of the exhaust emission sensor on the basis of the frequency response.
Naoya Fushimi
Yukari Hirano
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