I need to replace the 02 sensor on my 2001 V6 Mustang, but I have no idea where it is. Can anyone assist?

Thanks

 

Which one? There is at least 2. One before the cats and another after the cat. Theywould be on the exahust pipe, somewhere between the exhasut manifold and before the muffler. They look like a long sprak plug, threaded into the pipe on one end and wires coming ou the top.

 

You have 4, two upstream just after the pre-cats and two downstream right in the cats.