| 摘要 |
PROBLEM TO BE SOLVED: To detect element cracking of an air-fuel ratio sensor from a change in an output current from the air-fuel ratio sensor at a time of changing an applied voltage.SOLUTION: An abnormality diagnosis system for demarcation current type air-fuel ratio sensors (40, 41) disposed in an exhaust passage of an internal combustion engine, comprises: a current detection unit detecting an output current (I) from each of the air-fuel ratio sensors (40, 41); and an applied-voltage control unit (60) controlling an applied voltage (V) to each of the air-fuel ratio sensors (40, 41). The applied-voltage control unit (60) changes the applied voltage (V) in a range in which a demarcation current in response to an air-fuel ratio is generated when the air-fuel ratio sensors (40, 41) are normal when the air-fuel ratio is rich, in order to diagnose abnormality in the air-fuel ratio sensors (40, 41), and determines element cracking occurs to the air-fuel ratio sensors (40, 41) when the current detection unit detects a change in the output current (I) from each of the air-fuel ratio sensors (40, 41) by a preset value or more at a time of changing the applied voltage (V).SELECTED DRAWING: Figure 14 |
