2003 grand cherokee, 4.0L 6cyl. Battery is good, alternator is good, starter is good, etc...

when we take a short trip to the store, we will come out and it will not crank, will not click, nothing, no gauges, no lights... neighbor brings over his jump pack, hooks it up, and it starts right up. We even tried jumper cables before that and it wouldn't do anything. We let it run for 10 seconds, turn it off. With the jump pack disconnected, it starts right up immediately. So not the battery or alternator right??

When we hook the jump pack up, and put the key in the ignition for the first time, the gauges go crazy for a second, but it starts right up.

Is this some kind of module, regulator, or electronic problem that is causing this? It has happend multiple times now over the past few months... we even left it like this at home for a week while we were out of town, came back, tried to start it again, nothing happened (like when before we left), checked the battery voltage (12.2v), hooked up the neighbors jump pack, and it started right up - the odd thing is the ECU cleared the check engine light that was saved because it thought the battery was dead, but it wasn't ? (The CEL is for a rear o2 sensor)

Anyone have any idea what we can check next on this? Not the battery, alternator, starter, or any of that. Some type of electrical or connection issue? Any advice is greatly appreciated!!

 

Try cleaning the battery terminals before spending any money on parts.

 

If that doesn't solve the problem, try replacing the battery cable ends. I had one corroded inside the molded lead part of the end.