The 3.6L Wrangler will not run (start) if either battery is too low, or bad. Also, jump-starting is a longer process, since the AUX battery must come back up to normal voltage before it will start. Since the vehicle electronics need constant power through a stop-start cycle, they run on only on the AUX and the main battery cranks the starter and ignition. Battery charge voltage will fluctuage a lot too -- from 12V to 14V -- depending on what state the system is in. Most of this is in the Owner's Manual.I was just wondering. Does the Jeep still run if one battery dies?