That would depend on where the ground was bad IF it is a ground problem at all. Was just throwing it out there as a possibility.
Easiest way of checking a ground to the lights is to furnish a ground wire (piece of wire) from the neg of the battery and touch the turn signal housing (metal) one at a time to check each individual one with the circuit activated (ON) and see if it changes anything.
Other wise you have to go point to point through the circuit with a test light to see where the open is. The ground is the easiest to check, that's why I mentioned it first. After that it gets more involved. If it isn't something obvious, I would let the dealer handle the problem so there isn't any reprocussions when tinkering with the wiring.