Your scenario sounds just like mine. Other than coupe and no flashing lights. Parked the car one evening, next morning upon starting the car spoiler went up and ABS /BAS lit up. Car functions perfectly outside of spoiler and no ABS/BAS functions. I've replaced all 4 wheel sensors with known good used ones. Battery showed plenty of voltage, and eventually went dead about 8 months later. Can't see letting dealer throw parts at it, I can do that if I ever decide I want my spoiler functioning again.