not always so simple, Sparky... i'm having the same issue with my 06' rubicon and i've been doing a considerable amount of reading on the subject and the problem could be a number of things... i had a layered problem with mine, in that the dash was flashing two codes "no fuse" and "no bus". after fiddling with it all morning, stripping off all of my plastic, i found the cause of the "no fuse" (#26 in the fuse block under the hood that ties into about 8 different things) and it turns out it was my factory locker switch... but i'm still getting the "no bus" and i still have no communication to the OBD2 data plug, plus light stutter during idle as if misfiring or week-firing.
things its NOT, after ruling them out via my research:
1. loose plug on the back of the dash panel (cleaned with contact cleaner and gave them a slight twist.
2. broken or rubbing wire... i traced from PCM to the dash...
3. crank position sensor is working (seems to be the most comon associated problem if if flashes "no bus" and doesn't run, mine still runs)
4. throttle position sensor is working.
5. loose connection at the PCM.
6. bad cell in the battery or low battery voltage. i'm getting 12.4 across the board on every source i check.
other things things it could be:
1. bad dash.
2. bad PCM (had issues with this before actually, dealer fixable only since it needs to be programmed with VIN and mileage...)
3. short i haven't found yet
4. week or bad sensor i haven't ruled out yet.