| 摘要 |
<P>PROBLEM TO BE SOLVED: To determine discriminatingly determine a failure of an oxygen sensor and a circuit failure. <P>SOLUTION: This failure diagnosis device of an oxygen sensor generating an electromotive force corresponding to an oxygen concentration in exhaust gas is equipped with an element impedance detection circuit for detecting an element impedance of the oxygen sensor in a process for applying a voltage to the oxygen sensor and drawing it back, a sensor output voltage detection circuit for detecting an output voltage from the oxygen sensor, and an impedance reference failure determination means for discriminatingly determining a failure of the oxygen sensor and a failure of the element impedance detection circuit corresponding to at least the detected element impedance value when a voltage difference ΔVOX of the detected oxygen sensor output voltage before and after application is larger than a prescribed value. <P>COPYRIGHT: (C)2008,JPO&INPIT |
