Can a rear o2 sensor be used for the front o2 spot on a 5th gen? Thx!

 

They have different part #s, but I'm not sure if one can be swapped into the opposite position temporarily.

 

In theory, the answer is yes, but I don't know if they are "tuned" differently. The output is simple. If O2 is below 14.5% voltage quickly rises higher than .5v. Opposite for above 14.5%. The voltage moves from .2v to .9v with very little change in O2 - Some wideband O2 controller simulate the operation by sending either a high or low signal to the ECU via a switch.

The real answer is - I am not certain, but if they are not identical, they will be quite close and would work in a pinch. You will get an ECU error without the rear sensor, but it is not used in any way other, ie - it doesn't mess with your fuel mixture.