| 摘要 |
A method for preventing diagnosis errors of a down stream oxygen sensor is provided to distinguish fuel inferiority or inferiority of up/down stream oxygen sensors in case of abnormal operation of the down stream oxygen sensor. A method for preventing diagnosis errors of a down stream oxygen sensor includes the steps of estimating an oscillating frequency of an up stream oxygen sensor and a signal variation of the down stream oxygen sensor(S2,S4), and determining fuel inferiority or inferiority of the down stream oxygen sensor based on the estimated oscillating frequency and the signal variation when the down stream oxygen sensor shows abnormal operation. When the operation of the downstream oxygen sensor is shifted to a fuel lean state and a fuel rich shift does not follow by a predetermined bandwidth, the fuel inferiority is determined. When the fuel inferiority is determined, the fuel quantity control is prevented from being performed wrongly. |
