| 摘要 |
A method of determining the deterioration of an oxygen concentration sensor for an internal combustion engine. The oxygen concentration sensor includes at least one oxygen concentration sensor element having an oxygen-pumping element and a cell element each composed of a member of a solid electrolytic material having oxygen ion-conductivity, and a pair of electrodes having the member interposed therebetween, and a current-detecting resistance serially connected to the oxygen-pumping element to form a series circuit. A voltage having a magnitude corresponding to a difference between a voltage produced between the electrodes of the cell element and a predetermined reference voltage is applied to the series circuit, and pumping current is detected from a voltage developed across the current-detecting resistance. The predetermined reference voltage is changed from a first predetermined value to a second predetermined value, followed by detecting a difference between a value of said pumping current detected when the predetermined reference voltage assumes the first predetermined value and a value of the pumping current detected when the predetermined reference voltage assumes the second predetermined value. It is determined that there is deterioration in the oxygen concentration sensor when the difference is equal to or greater than a predetermined reference value.
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