Techies' Law understood!

The car was dropped off at the dealer minutes ago for a diagnosis.

If the wiring harness is bad, will the codes matter? I've been told by other M104 owners that when their harness went, they got a bunch of whacky codes that could not be trusted. In fact, I've also been told that some Indy shops won't even work on the M104 if the wiring harness hasn't been replaced since the codes thrown may or may not reflect the true problem.

Please shine some much needed light on this issue.

Thanks so much for your help guys!!!