| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress the deterioration of the determination accuracy of an imbalance failure irrespective of a form of the deterioration, and to execute exact determination, when a response characteristic of an air-fuel ratio sensor is deteriorated. <P>SOLUTION: A vibration signal is generated by using a first signal of a first frequency f1 being a frequency which is a half of a frequency corresponding to an engine rotation number NE, and different from a 0.5-order frequency fIMB, and a second signal of a second frequency f2 higher than the first requirement f1 and different from the 0.5-order frequency fIMB, and air-fuel ratio vibration control is executed by using the vibration signal. During the execution of the air-fuel ratio vibration control, 0.5-order frequency component intensity, frequency-f1 component intensity and frequency-f2 component intensity which are included in an LAF sensor output signal are calculated, reference component intensity is calculated according to first and second frequency component intensity, and the imbalance failure is determined on the basis of a relative relationship between the 0.5-order frequency component intensity and the reference component intensity. <P>COPYRIGHT: (C)2013,JPO&INPIT |
