I have a 2005 GMC Yukon and whenever I apply the brakes and have the blinker on the blinker goes crazy and i lose both brake and blinker lights. Whenever the headlights are on, I have no back lights period (blinker, brake, reverse). I have checked the fuse box, both underneath the dash, and inside the engine compartment. I have checked the ground wires and the bulbs. Everything is good so far. Anyone know what might cause this? I was told it might be the flasher module, and could just needed to be reseated, but do not know where it is. Anyone know what's going on?