AFS105 O2 sensors
 

I need to replace my downstream O2 sensor. Is the AFS105 from AC Delco used in all three locations? I have one but I bought it when I thought I had an upstream sensor go bad.

Yes, the ACDelco AFS105 Oxygen Sensor is listed as a pre and post cat converter sensor.
I always like to put the new ones up front and move the old ones to the back.

Well I just did a tune up Delco plugs, wires, cap, rotor, ETC. I had a fuel pump go out and few weeks later had to replace the spider. I did the intake gaskets since I there. I found a place online selling the AFS105s for $30 a piece I have 1 so I think Im gonna just replace all of them and be done.

Even better thanks