Plug Where does it belong

Hey, guys.
I happened to see a cable hanging out under the engine. I'll be right on stage and the search started. I found nothing on the bottom and side.
The length and shape of the cable gave me the idea that the thing must have fallen from the top back. Before I start to remove the filter box and other covers at minus 8 degrees, I'll check with you.
So almost everything works. No alarm no failures of the on-board instruments... only .... the autopilot has not been working for three weeks. It's obvious that the plug is here somewhere.
In the appendix is a bilge from the plug. It is "lockable" The wire colours ( 2 pole) are green and grey or lilla. Not quite cleanly recognizable.
Who knows this thing?
Winter greetings
Ruedi