2021 Tahoe High Country 6.2l 13,700 miles, new engine at 7000 miles for bent push rod/lifter issues.

Got a message from OnStar on my cell phone yesterday evening saying battery voltage was "critically low", didn't see the message until 7:00A this morning. Went out this AM and the vehicle was grave yard dead. I put the battery charger on for the day, after 8 hours the charger was still showing 5A. Drove the Tahoe a bit, noted the volt meter stayed at 14v and noted the check engine light was on

Advance Auto scanned the OBD-II - came up with the following codes:
P25A - No DTC Deff Found
P0562 - System voltage low (duh)
P0606 - ENgine control module powertrain control module
U3006 - Control Module Input Power A
U3007 - Control Module Input Power B

Called dealer service about 4:45 this afternoon, left a message, of course no return call

Wondering if anyone else has had similar experiences. It's obviously warranty repair, just curious about any others with similar.

 

 

11/19/2021 Update: Drove the Tahoe around some, maybe 50 miles, check engine light is now out, battery is charging. Dunno what drained the battery, guess I'll continue to monitor. I may use the multi-meter to see what the draw is when the vehicle is just setting and not running. Right now everything seems to me back on line. Hopefully it was nothing but a random event.

 

Intermittents are tough. Much easier to fix when it goes bad completely.

2016 Mrs. Cusser had stall on my 1998 Frontier, could not get it restarted, and neither could I once I arrived; had AAA tow it to my home. I didn't check for spark first, added aerosol starting fluid and within a minute was able to get it to start, had check engine code. I drove it to O'Reilly and Autozone, both read code as bad distributor or distributor internal coil. Well, 5 years later check engine light never returned, truck runs fine (never happened again), same distributor coil. Reliable truck, have no idea what went wrong.

 

when a battery slowly goes dead the vehicle modules will not shut down properly and loss of communication codes will set...u codes. low voltage codes will set also and let the tech know why all the comm codes set; meaning the loss of comm was a voltage problem and the can bus com system is not at fault.
fully dead batteries will take more than 8 hours to charge at 5amphour rate.

fully charge the battery and have the battery tested.
check for anything left on...aftermarket devices that could create a draw.
perform a parasitic draw test

 

A parasitic draw test is a good thing to do, Google on how to perform and recommended typical draw. The ECU/computer and the clock/presets for stereos can be small draws on vehicles, maybe on these newer integrated systems all is in the ECU.

On my 2004 Frontier, can easily go 2 months and start right up...

 

Relays can intermittently stick closed. Tough to diagnose unless it's happening while your testing. My '11 had a dead battery one morning, never happened again. Battery was about 5 yrs. old and it performed fine until I changed it out at 7 yrs. due to age not performance. Still using that factory battery, on a BatteryMinder, to power lights in my pop up last summer.
Decades of appliance repair taught me on higher amperage relays sticking as arcing in them is more pronounced and burnt contacts are more common, it's nice when you can ''tap'' one and see it release. Now if they had clear housings so you could see the contacts that would be too easy.

 

I have the same issue now. Any thoughts?

 

@dc3873
Please avoid "me too" posts.
Post your vehicle info, the exact symptoms you're experiencing, and any troubleshooting you've tried. Ideally, in a new post instead of reviving old ones. Thanks.