Did you figure out what caused your problem, mine is doing the same thing
May, 28, 2011 AT 5:23 PM
I have the same problem and my research found this possible solution http://www.fixya.com/cars/t5911682-2007_buick_lacrosse_low_beam_headlights they say it's the exterior lighting relay somewhere underhood in the engine compartment. Other have said there are multiple relays in there so I am still looking for information as to where the location is for the headlamp relay. If you find out please update this post thread. Thx.