The red plug should be under your rider seat but from your photo it's obviously not there.There is NO plug to install on my new GS.
Just asking......
Check you documentation pack you got from your dealer, maybe they took it out and put it with all the paperwork.
Or check this video on how to fit the plug, maybe they've done this already
. This is for the 1200 but is the same for the 1250.

