2002 trailblazer says powering down and shuts off

I have a 2002 trailblazer with the V6 engine. while driving it will say on the message center POWERING DOWN. the engine shuts off and after coasting to a stop its like the battery is dead. It wont shift into park and the key cant be removed from the key switch. thinking that it was a battery or alternator problem I had both replaced. And it done the same thing the last time it was driven. Had it towed home, connected a battery charger to it to boost it and it allowed me to cut the ignition to the off position and remove the key.

What could be wrong with it?

I have a 2002 trailblazer with the V6 engine.
Didn't know they put a V-6 in the Trailblazer. I learn something new every day.

while driving it will say on the message center POWERING DOWN. the engine shuts off and after coasting to a stop its like the battery is dead. It wont shift into park and the key cant be removed from the key switch. thinking that it was a battery or alternator problem I had both replaced. And it done the same thing the last time it was driven. Had it towed home, connected a battery charger to it to boost it and it allowed me to cut the ignition to the off position and remove the key.

What could be wrong with it?
What is the battery voltage when running at fast idle or higher?

I6 4.2 DOHC engine assuming this is the new TB not the s-10 version. Either way the electrical system and charging system must be gone over.

The TB isnt mine it belongs to a friend, anyway, she said the voltage meter goes from 14 down to 5 and it starts flashing powering down on her message center. what ever is wrong it completely kills the battery, the interior lights wont even come on its so dead. . also she said some time ago her rear wiper motor had to be disconnected because it kept coming on and wouldnt go off.

If this happens when running, there is either a heavy dead short somewhere or the Alt is no good.

It has a new Alternator, belt and a brand new Delco battery both from Chevy dealer, I'm starting to think maybe its starter is grounded, or possible a steering column, or key switch problem

If the headlights, heater/blower running, and come to a stop its kills the motor, something's zapping the battery and shutting everything down

Won't be the first time a "new" alternator failed.....was it doing this BEFORE the vehicle had the new alternator put in? If yes, how long after the alternator was put in did it fail?

In any case, the electrical system has to be checked out......voltage has to be observed while a load is put on the engine...

Tech II it was doing the same thing, the new stuff has already been checked there is nothing wrong with the alternator. I guess we'll have to just start traving the wiring starting with the battery cables and check the starter I was told the cylinoid could be stuck in causing it to drain the battery

Even with a large drain the 140a alternator should be able to keep the car running unless it was an unprotected dead short, which would most likely start a fire.

Find out the system voltage at the point where it tells you it's shutting down.

Everything else is guesswork and assumptions.