The multi-plex unit is the "hub" for most (if not all) wiring traffic. I think there are both a driver side and passenger side unit. And as stated as such, each will handle whatever electrioncs (and maybe others) are on each side of the vehicle.
So yes, it does make sense that if you are experiencing problems on the driver side, it could be the driver side multi-plex unit. But I will let the other gurus handle you Roger.

Cuz I'm not entirely sure.