Patent ID: 6205989
Filing Date: 2001-03-27
Classification: F02D

Abstract:
A control device for an air-fuel ratio sensor based on a current from an oxygen concentration detecting device, the current corresponding to a concentration of oxygen in a gas when a voltage is applied to the oxygen concentration detecting device, the air-fuel ratio sensor control device comprising:means for detecting an alternating impedance of the oxygen concentration detecting device corresponding to each of a plurality of frequencies applied to the oxygen concentration detecting device, the impedance detecting means applying to the oxygen concentration detecting device alternating voltages of two different frequencies selected from the plurality of frequencies; andmeans for analyzing the detected alternating impedance corresponding to the to a plurality of frequencies to calculate a parameter indicating a change over time of a characteristic of the oxygen concentration detecting device, wherein the parameter calculating means calculates the parameter based on a difference between the alternating impedance of the oxygen concentration detecting device corresponding to two different frequencies selected from the plurality of frequencies.