Haven car problems

It probably because you had the battery disconnected, should just have the code reset. This is what the code means...P1684 DODGE - Battery Power To Module Disconnected... Possible causes... - Battery was recently disconnected - Transmission Control Module (TCM) was replaced or disconnected - Faulty Transmission Control Module (TCM) - Transmission Control Module (TCM) harness is open or shorted - Transmission Control Module (TCM) circuit poor electrical connection... Some Tech notes... If other codes are present, check and repair other codes first. Make sure the battery charge is OK and the battery connectors are firmly secure... When is the code is detected... This code is set whenever Transmission Control Module (TCM) is disconnected from battery power B+ or ground. It will also be set during the DRB III Quick Battery Disconnect procedure. Possible symptoms... - Engine Light ON (or Service Engine Soon Warning Light)

The cure for that one that I have found is new battery. First time was on a 98 Dakota that wouldn't idle without foot on gas. After a few weeks I left the radio on, battery croaked. Put in new battery, ran like new. Run into it a couple other times. PCM detects low voltage and sets a code.

That all fits & makes sense...

What would make my car die while its running its happened to me 4 times today

PCM not getting enough voltage to keep all the electronics running.

What does pcm stand for?

And how do I fix it

Powertrain control module. It's the cars computer. Dodge calls them a PCM because they control everything to do with the enigine, transmission, and, etc

I'd put a new battery in it.

OK what if that don't fix it then what should I do