The headlights/lamps on our 2003 GMC Envoy XL are shutting on and off by themselves. This is regardless of what option is selected on the exterior lamps knob. Automatic or Headlamps. Both headlamps shut off and come back on together. All at random times. Sometimes when starting the car they don't turn on at all. Any ideas?? Thanks.

It sounds like there might be a short somewhere in the system. I have heard of this happening before, I just don't know where you would begin to look.

Look at relay 46 in your relay box under the hood. Swap it with the identical one next to it. That will stop your lights from turning off for no reason. If that works you should eventually replace the relay. Unfortunately, you can only get them at a dealer for about $45 each. You could try a junkyard, though.