Find junction S212, take the nut off and find out which of leads the current is flowing to.
Yea, not gonna be easy to find... Damn.

I believe S212 is under the fuse panel, you pry the platform the fuses sit in from the front of the fuse box, lift it up and away.
Underneath, there are a few studs with a lot of wires on them. ONE of them is S212. This post is also called out in the service manual but I cant find it right now.