Originally Posted by jliltd
Wow. I hope the first shop wasn't a Garmin dealer. That's avionics data bus 101 to wire serial signal wires per the manual.
It most definitely was! In addition they said they mimicked the RS232 feed into the GTX and that the GTX was bad.
***Update- I wired back in the harness and it still didn't work. Called the 2nd shop and they said they found a G5 to test the GTX with and to bring it back. I then pulled my G5 (just in case) and took everything back. They hooked it to the good G5 and it "worked"!! Yes.... Finally know the issue.
We will see if mine is in warranty and ship it back to be fixed Monday. Can't wait! Blue skies and no transponder sucks! I'm under a Bravo so need the Mode C.