Umm, not quite sure what you're getting at here.
The pre-cat and post-cat sensors are the same model (AFS75), so they can be installed in either position.
However, if you are asking if the post-cat O2 sensor will do the jobe if the pre-cat sensor is fried, the answer is no. The pre-cat sensor is used for adjusting the fuel trim, the post-cat sensor is only used to monitor the function of the catalytic converter.
The pre-cat and post-cat sensors are the same model (AFS75), so they can be installed in either position.
However, if you are asking if the post-cat O2 sensor will do the jobe if the pre-cat sensor is fried, the answer is no. The pre-cat sensor is used for adjusting the fuel trim, the post-cat sensor is only used to monitor the function of the catalytic converter.