Re: Dell XPS 15 (L501X) Conrtol Strip Not Working..HELP!!
It sounds like the power button board has failed. If you are out of warranty you may consider replacing it. The following link is to the service manual and gives instructions in removing the power button board.
<ADMIN NOTE: Broken link has been removed from this post by Dell>If the system is under warranty and you have not spoke to tech support about it yet, shoot me a private message with your contact info and the service tag and I will research possible service options.