According to the manual for my 2004 fuse 1.2 handles the IVD stop lamp relay, brake pedal position switch and the turn signal relay.
Those 3 are all in different locations. The brake pedal position switch is on the brake pedal. The turn signal relay is slightly to the right of the parking brake. The IVD stop lamp relay is under the hood, here's the diagram for the IVD relay.
I don't think there is a single ground that would effect all 3 and not other things. Here's a list of the grounds though. I went through my grounds not long ago in troubleshooting and found only 1 that was bad. G400 located inside the driver side frame rail next to the spare tire.
