| 摘要 |
PURPOSE:To obtain a failure detecting device of an air-fuel ratio sensor, by which a failure of a first air-fuel ratio sensor can be detected surely. CONSTITUTION:The output signal period of a first air-fuel ratio sensor is detected by a period measuring means B101, the period is compared with a designated value by a first determining means B102 to determine a failure in the first air-fuel ratio sensor when the period is larger than the designated value, and the controlled variable from a second air-fuel ratio sensor is compared with a designated value by a second determining means B103 to determine a failure in the first air-fuel ratio sensor when the air-fuel ratio controlled variable is larger than the designated value. Accordingly, the failure of the air-fuel ratio sensor can be detected surely so as to properly control the air-fuel ratio.
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