So I'm having an issue with the lights in my 2005 GMC Sierra 1500. The dash lights, heated seat lights and even the headlights will flicker on and off. Sometimes if you hit a bump it will make them go off or come back on. Every once in a while the headlights will flip off and then right back on. But... the gauges work, the window, lock, and heated seat switches work even when the lights don't. The switches on the steering wheel work and the radio dials, heater switches on the dash... everything still works. The only things affected are the lights. You can push the dimmer dial and even right above the dimmer dial and the lights will come back on. And sometimes you can smack the dash and they'll come back on. Lots of info but I'm hoping someone can help me figure this out. Oh, and the service engine light never goes off even when the other things do. Any thoughts??