No answer back yet from Garmin on Config setting for ARINC RS 232 connections. I decided since I was getting similar error messages before and after redoing wiring from GNX375 to GDU 460 per page 109 of GNX 375 install to diagram on page 24-37 G3X ver AQ install manual, I decided i had a wiring error. Sure enough, I had some wires cross between GAD 29 and GNX 375.
Originally thought I would have to pull out entire instrument panel to access connectors. After removing all avionics and just a few panel support screws, I saw I could access the pins at back of GNX375 mount using jumper pins. Spent 6 hours trouble shooting, pulling pins on connector on GAD 29 and repinning to match wiring diagram located page 24-37 on G3X install manual ver AQ. During the process, i reconfirmed correct pin continuity between GDU 460 and GNX 375 were/are as shows on page 24-37 G3x install manual.
Pleased with my self, I put all back together and fired up config screen. Good new is I had another connection show up but still with couple Red X's with ARINC and RS 232 connections......very discouraging.