So my 2008 GMC Sierra 1500 work truck has been having quite a few electrical issues. My cruise control usually does not turn on(ocassionally it will), my lock/unlock switch on the door doesn't work, a few of my climate control dash lights don't work, and my brake lights have been staying on while I drive. (No the parking brake is not on). I also have a headlight out but I think that is just a dead bulb. What could be wrong? Is there a common denominator? Truck has about 80k miles on it. Any ideas at all? Thanks.