From what I can tell there is only one but I just wanted to make sure before I replace it. It seems the only one I have is right before the cat. So my question is: is it one or two on a 95 4Runner 3vze non- california model?

 

ONE in front of cat.
96 up vehicle ODBII have 2 sensors, one in front one behind cat.

 

Thanks, that's what I thought, just wanted to make sure. I'm getting 13.5 mpg around town right now so I hope this helps.