2014 1500 suddenly died on interstate

[Jeepwalker]

There's a lot not making sense in your description. Probably a few things you heard incorrectly, or having a hard time piecing together what they said ...but that's ok.

I think instead of losing compression, the mechanic was indicating it lost 'fire' or 'spark' to all the cylinders. Or fuel. ...basically lost 'electrical power'.

That comes down to what some of the other guys were saying ...there's a metal piece which acts like a 'fuse' off the battery cable where the cable attaches to the fuse box. check that. There could be some other simple causes ...like:

1) The battery simply failed. Very likely. And when they do, they make the vehicle act like it's 'possessed'.
2) The WIN module simply failed ...basically an electronic box which acts like the on/off switch (only a lot more complicated with circuits ...and a known item that can fail). Or another main wire or fuse.
3) Some main wire failure (cable??)
4) Main fuse failure
5) Sudden computer fail.

Always start with the simple, easy and cheap things first bc that's usually what it turns out to be. Don't let them talk you into a new computer right away. Start with the fuses and verify operation of the battery. Are these Mechanics any good?

 

[Jeepwalker]

I edited my post above... perhaps re-read for greater clarity

 

[revkevin]

The one thing that everyone (mechanics, forum members, and friends) seems to agree on about everything from how I described the original issue to the various theories different mechanics have thrown out, is "This doesn't make sense." I even talked with the guy riding with me when it died to make sure I was describing what happened correctly.

 

[Ken226]

The throttle body is operated electronically, no cables.

When some communication problem or electrical fault results in the electronic throttle control out of commission, it has a similar effect to having low compression.

On our engines there is no IAC valve, the PCM controls idle speed by holding the blade at a specific setting, so during a crank/no start the fully closed throttle blade makes the engine rotate faster, as if there is low compression. If your mechanic wasn't aware of this, it likely fooled him.

If you hold the blade open a little with your thumb and crank, I bet the compression will sound pretty normal.

It sounds like you need a mechanic who is good at diagnosing electrical faults.