| 摘要 |
PROBLEM TO BE SOLVED: To prevent the lowering of detection precision for an oxygen concentration by shortening a time coefficient of an element impressed voltage for detecting an oxygen concentration sensor element impedance. SOLUTION: A sub-microcomputer 56 conducts at least twice times sweep processing for switching an element impressed voltage Vo from a reference voltage to a sweep voltage, when an element impedance of an oxygen concentration sensor AFS is detected once, and a time coefficient per one time is shortened by A/D-converting only either of the voltage Vo or an element current detecting voltage Vi during one sweep. Since a sensor drive circuit 59 controls the voltage Vo not to vary by an element current (oxygen concentration), even when detection from the voltage Vo and detection for the voltage Vi and carried out by separate sweeps, an detection result substantially same to that in the case, where the detections for these two voltages are conducted during one sweep is provided to detect the element impedance based on the detection result. |
