Patent ID: 6136169
Filing Date: 2000-10-24
Classification: F02D,G01N

Abstract:
An abnormality diagnosing apparatus for an air-fuel ratio sensor system of an internal combustion engine which detects an air-fuel ratio of mixture by flowing a current of an air-fuel ratio sensor through a current detecting resistor and detecting a difference between two voltages appearing at both ends of the current detecting resistor, the abnormality diagnosing apparatus comprising:activation determining means for determining whether the air-fuel ratio sensor is in an active state; andabnormality diagnosing means for diagnosing the air-fuel ratio sensor system for a presence/absence of at abnormality from a combination of results of predetermined comparison processings made separately with respect to each of the voltages appearing at the ends of the current detecting resistor, only when the air-fuel ratio sensor is determined to be in the active state.