Wiring issues are not uncommon and they can be the hardest problems to fix. Most transmission rebuilders are not electricians although there are exceptions. Most shops will have a designated person that diagnoses all electrical problems. Some shops actually sublet their more complicated wiring issues to another shop.
When diagnosing an electrical problem on a modern day vehicle, the tooling and training required can be quite extensive. You should be prepared to pay at least 2 hours shop labor rate to isolate your electrical problem.
