Air-fuel ratio sensor resistance detecting apparatus

An apparatus for detecting a resistance of an air-fuel ratio sensor comprising:

• an oxygen concentration detecting element, a current flowing through the oxygen concentration detecting element being proportional to an oxygen concentration of a detection object gas flowing over the oxygen concentration detecting element;
• a heater for activating the oxygen concentration detecting element;
• an air-fuel ratio detector that detects the current flowing through the oxygen concentration detecting element by applying a first voltage to the oxygen concentration detecting element, the air-fuel ratio detector detecting an air-fuel ratio of the detection object gas based on the detected current;
• the first voltage being a DC voltage;
• a gas condition detector that detects a condition of the detection object gas;
• an impedance detector that detects an impedance of the oxygen concentration detecting element by applying a second voltage to the oxygen concentration detecting element, wherein the second voltage is obtained by superimposing an AC voltage on the first voltage;
• correction means for correcting the impedance detected by the impedance detector, in accordance with the gas condition;
• and
• a controller that controls the electrification of the heater based on the impedance corrected by the correction means.