Adaptive charging system won't drop down to 12v

[GMC2018]

I'm not sure how far ill get with this but here goes. I have a 2018 GMC Sierra 1500 5.3L C engine code non flex. Its got 20k on it when i bought it had a crappy napa battery in it but the adaptive charging system worked fine with the napa battery it would be a 14.4 volts on start up and then drop down to 12 as it should and the back up to 14 per the conditions listed in the service info well i replaced the 94r napa battery with a 94r oriellys agm battery and the voltage would inky stay at 14.4 not drop down to 12 when electrical loads are low so i hooked up the scan tool at my shop and see that according to the BCM the battery was at 67%charged (all other data was normal and in the right conditions for the charging sytem to drop down to 12 volts) but the state of charge has to be at least 80% so i tried charging the battery and state of charge on the scan tool never changed so i attributed it to the fact that i put an agm battery in the truck and the BCM didnt like this so i went and exchanged it for a non agm 94r battery and intalled it well after driving it for a bit the charging system still did not drop down to 12 volts despite low electrical load. Ill hook the scan tool back up tomorrow and see what the BCM thinks the state of charge is but has anyone else encountered this? Thanks.

Edited June 26, 2020 by GMC2018

[lonestardiver]

Deleted...

[Snowcamo]

You so don't have an issue... I never really see it 12v either. It'll do as its supposed when the time is.

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[Roberto Donoso]

Hi. Here from Chile. I have the same issue. 2014 Silverado LTZ crew cab 1500 and suddenly the GM Smart charging system doesn't works. It's fixed 14.9 - 15 Volt. I changed alternator, ground cable with battery current sensor and battery. No change. I scanned several times and no DTC'S. Scanner display battery charge 65% and the BCM is command 80%. The next step, i Will look for a disrupt wire at side of PCM. Sorry for my english. I pulled up the battery current sensor connector AND not changes. I thinking is a wire shorted or the BCM

 

[zachdill5]

On 11/21/2021 at 6:17 PM, Roberto Donoso said:

Hi. Here from Chile. I have the same issue. 2014 Silverado LTZ crew cab 1500 and suddenly the GM Smart charging system doesn't works. It's fixed 14.9 - 15 Volt. I changed alternator, ground cable with battery current sensor and battery. No change. I scanned several times and no DTC'S. Scanner display battery charge 65% and the BCM is command 80%. The next step, i Will look for a disrupt wire at side of PCM. Sorry for my english. I pulled up the battery current sensor connector AND not changes. I thinking is a wire shorted or the BCM

 

did you ever figure this out?