There's a thread where you can request wiring diagrams from a member. You'll need to provide contact info, of course. Then you'll be better able to track down where the issue might be.
It sounds a lot like the key circuit failed. At this point, pull every fuse and check it, both visually and with a meter. Tedious I know, but it may reveal a "good" fuse that isn't so good. It'll also provide a chance to make sure the contacts are in good shape, not black or discolored from corrosion. And you can use some contact cleaner and dielectric grease if you want to give 'er the beans.
If you need A wiring diagram for your 2000-2005 Lesabre I have more than likely every diagram you could need for it found a site for 15 bucks that seems like it covers everything on that car you can message me with a email and I can send the entire catalog to you in zip file or I will leave the link I got them from and you can get them that way up you but figured no since in everyone having to buy them when I already paid for them and can send a copy to you here is link if it pops up black screen saying verifying your connection just wait till it give you the check box it and it will take...
