I have a 2005 buick lacrosse with 32000mi. With the 3.8l v6. Over that last few weeks, My daytime running lights have been shuting off while im driving and wont turn back on and while I was driving to work this morning in the dark, about 10 min into driving they shut off. I tried to turn them back on manually by switching my lights from auto to on but they won't turn back on, about 20 min later when I got to work they decided to turn back on. Every time this happens no matter what I do I cant get them to turn back on and Im forced to use my high beams which don't seem to be affected at all by this. Im wondering if this is a computer problem. I don't think its a fuse because they go on and off and I checked the fuses and their all fine.
I was looking at the schematics and it looks like the Body Control Module is what pulls the curcut to ground. There is a headlamp module(relay) in the underhood fuse box it only controls the lowbeam lights. It is relay #35 You could replace that and see if that takes care of your problem. If that does not do it then You would need to lean towards the BCM or a wiring issue. Is the car ot of warranty?