front and rear oxygen sensor the same?

[bluebombersfan]

I went to Canadian tire to get an oxygen sensor and the guy told me that the front and rear are exactly the same. I checked autoparts online and they also seem to be sold as the same item.
My problem is I'm reading a OBD2 techbook and it says that the upstream and downstream oxygen have different jobs. The upstream sensor monitors the oxygen level and tells the pcm how fuel is needed, the downstream oxy sensor after the cat from my understanding just reports that the cat converter is working properly.
So how is the same sensor suppose to work for two different functions?

 

[Frank The Tank]

It makes sense. They have different jobs.
One adjusts fuel ratio.
One sense that the cat functioning, not plugged or missing.

They are reading for the same information, only they have different functions to react to them.


I know what I want to say, but I'm struggling with the words.

Frank

 

[bluebombersfan]

With some more reading I found out the same thing that a properly working cat converter somehow converts or removes any oxygen left and if the downstream oxygen senser detects to much oxygen a code will set that the cat is not doing its job,