Car appreciation... the aesthetics, the engineering, etc

On that diagram the brown earth return from the horn contact goes through the airbag slip ring if you look at the little tag wire off of it there is a box with a number in it (I cant read it too pixelated but looks like M110) that probably refers to another diagram for non airbag type or an image of an earth location

Edit just found this image, some Porsches have a link wire from rack to subframe where they have rubber mounted racks, worth a look, just run a jump lead from the rack to earth and see if you get what you need.