Hi all, I just registered on this site today to get info on this EXACT same issue, which is driving me nuts!
2015 Fusion, bought a couple months ago from Carmax with about 38K miles.
Creak/tick coming from rear passenger area, fairly sure that the plastic piece on the running board inside the doorway is at fault. Only happens at highway speeds. Pushing on the plastic molding definitely produces a creaking noise, whereas driver side rear molding does not creak.
Thinking of taking to the local Ford dealer tomorrow to see if it can be replaced. Unfortunately this one issue is ruining an otherwise perfect car for me, so I really hope it can be fixed.
