3x9 manual.Here's a pic of same area of my 2007 TC30 - no mystery plug. Is your tractor hydrostatic transmission? Mine is manual.
I believe now you are correct. I was confused, because I had the safety controller dismounted from the firewall, in a attempt to unplug/reseat the connector, thinking the safety controller is causing the no-start condition. In that effort, I had to dismount that black shrouded connector, which controls the flasher device, to get to the safety controller mounting screws.Found your missing part, #1