I replaced the key switch now my Yukon will start and die I need to know how to reset the anyi thief system

Nope!!! Got to use original key to do that!!! All that's been changed now so that won't work!!! Ok, by looking at your profile, I see you've got this same problem with your Yukon and that proceedure was suggested for you to do, .. SO.. tell us...Did it work on yours? ..'NO'.. So why did you even bother to post that???