I have a 2004 Grand Prix GT2 - 108k on it. The cruise control intermittently would work off and on. I read to check the third brake light - and sure enough it's out. BUT I tested it up to the wiring harness in the trunk and it does work off of a car battery. Is there a common switch / wiring that could go bad leading to this? I replaced the brake switch and it's not that. Anyone know what color wiring and where I should look first? Fuses are all good.