| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an abnormality diagnostic device which is suitable for an oxygen sensor having a diffusion layer in an outer layer part of a detection element. <P>SOLUTION: At least one of a plurality of positive direct currents obtained when a plurality of positive direct voltages different in magnitude are applied to the detection element; and a plurality of negative direct currents obtained when a plurality of negative direct voltages different in magnitude are applied to the detection element is detected. Based on a change rate of the detected direct currents that is the at least one of the plurality of positive direct currents and the plurality of negative direct currents, it is determined whether the oxygen sensor is normal or abnormal. Diagnostic errors can be reduced by reducing the influence of variations in current values caused by the variations or the like in the detection element itself. <P>COPYRIGHT: (C)2012,JPO&INPIT |
