Remove the inside door panel and see what has happened. Only then will you know the problem.
you will have to replace the window regulator.
If you heard a pop noise and then the window went down on its own, the regulator has failed.
kick it
If the window regulator cable has failed, the entire regulator will have to be replaced.
You need a new window regulator assembly. About $100 at the dealer.
what is the average repair cost to fix an electric window switch motor 2003 jeep
I've included a link below in related links that will show you a YouTube video on How To fix the window regulator for your 99 Jeep Grand Cherokee.
Replace the window regulator
my electric windows on my Cherokee jeep won`t work. WHAT can i do to solve this
A big fat needle, and some waxed string or thread.
take it to the dealer!!