Welcome to 2CarPros. Over time it will drain the battery and it also gives people the idea you are turning, that could lead to an accident. Looking at the wiring diagram it seems that the front module controls the mirrors so they are more or less independent items from the rest of the lamps.
The other left turn lights are off correct? In that case it could be a short in the wiring to the mirror in the door. Testing would be to remove the door trim panel to access the wiring and test the wires to the mirror.
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Tuesday, October 1st, 2019 AT 8:59 PM