| 摘要 |
PROBLEM TO BE SOLVED: To execute abnormality detection of a sensor, even in a operation state having possibility of reaching an element temperature, at which a sufficient element activated state cannot be maintained in an air-fuel ratio sensor. SOLUTION: An element impedance Z of an air-fuel ratio sensor is detected, for example, in the fuel cut-off state, namely in the state where the air-fuel ratio ought to be larger than 18 (104). Then, an element temperature T corresponding to Z is obtained (106). Then, a current value to be outputted from the air-fuel ratio sensor when the element temperature is T and the air-fuel ratio is 18, is calculated as a criterion value IR (108). Then, a present actual output current value I of the air-fuel ratio sensor is obtained (110). Then when I<IR (112:Y), namely, when the air-fuel ratio sensor is showing air-fuel ratio of less than 18, the sensor is decided as being sensor being abnormal (114). |
