First thing to check is your fuses. Don't start modifying your ECU before you have ruled out other causes. Find a wiring schematic and find out if you can hotwire the Jeep to start (it's not hard and only requires one wire). If you can, then you've got a bad fuse or fusible link somewhere.
I had the same problem once. Turned out to be corroded fuses.
”This year will go down in history. For the first time, a civilized nation has full gun registration. Our streets will be safer, our police more efficient, and the world will follow our lead into the future!” ~Adolph Hitler, 1935, on The Weapons Act of Nazi Germany