I had my car at a dealer garage this past week for a few problems. The supervisor explained that one of the problems was a bad wire in the wiring harness. He told me the wiring harness is "no longer available," not even as an after-market product, and that they'd have to go through and test every wire in the harness since they can't replace it as a whole.

That seems a little odd to me. Is it true?

 

In all my years as a tech, I only had to replace a couple wire harnesses and they were all do to an engine fire. it is very rare to need a wire harness AND a PCM like your 2 questions.

 

Sounds like the dealer was lubing you up for a bend over. If they knew there was a bad wire, they would have known which wire it was. Most likely, a dirty connector. Unplug each connector and clean them out and re-seat them. Too many dealer service departments like to rip off customers, just like the government does.