FAULT PREDICTING DEVICE FOR OXYGEN SENSOR

摘要

PURPOSE:To facilitate dealing with maintenance by comparing the peak-to-peak voltage of an oxygen sensor and the threshold value corresponding to a feedback control period and detecting the deterioration stage of the oxygen sensor. CONSTITUTION:A means 3 for computing the peak-to-peak voltage computes the peak-to-peak voltage VPP from the output of the oxygen sensor 1 which outputs the voltage changing sharply with the theoretical air-fuel ratio as a boundary when the feedback control region of the air-fuel ratio is decided by a means 2 for deciding the feedback control region. This voltage is inputted to a means 5 for deciding the deterioration of the sensor. The means 5 compares VPP of a means 4 for setting the threshold value and the threshold value determined in accordance with the feedback control period and decides the deterioration of the oxygen sensor. The detection of the deterioration in the stage not to the extent of a fault by the self-diagnosis is thereby enabled and the treatment appropriate for the deterioration of the sensor is facilitated.