So our Cat 865B get a fault code #118 I believe, and it will not allow the system to auto steer.  Lightbar, signal everything else works fine.  Over on the Cat TMC display I am getting an active fault 820-2 and one other one.  When the TMC is turned straight down to the Guidance mode it is thinking it is "running the show" instead of letting the Trimble system.  It used to always say "Not Installed" previous to this new problem arising.  It occured just after shutting down to fuel when I went to restart.  Took lower right side of inside of cab apart and stared at numerous wiring harnesses and made several phone calls, to no avail.  It is something to do with a "Communications error" of some kind.  Tractor will not clear active error so trimble system is detecting a fault that needs to be cleared.  Sorry to ramble, any help of any kind is appreciated.  I did some reboots and looked at harnesses and yellow and green wires, etc.  Thanks in advanced.  Dealer went to Wyoming may be 5-6 days before he can look.