It sounds like a Crankshaft Position Sensor (CPS) The Jeep will not run or start if it is bad. This sensor is located on top of the bell housing (transmission), usually with one bolt, it sits inside the bell housing similar to a spark plug hole except, no threads just pressed into the hole. has a 12 inch electrical connection attached, cost $35-$45 and 15 minutes to change out very easy, they go out all the time. Google the part and you will find schematics and diagrams showing exact location. New sensor comes with a small pad attached to end of sensor, make sure pad is in place before you install it. Do not go to a repair shop, save your hard earned money, very easy to change. Change this sensor out before you think there is a problem with the fuel filter or fuel pump, they almost never fail on Jeeps, usually something simple like this sensor.