4 year old battery???

Yes 2017 was the last time I remember replacing the battery.

Battery voltage is at 12.24 volts when the truck is off. I have not gotten it tested yet.

Yes get it load tested as these were subject to frequent battery run down issues.
There were also major issues regarding the active fuel management system with lawsuits involved.
This site is very interesting & GM may have a known issue listing regarding stalling or engine cut outs.
https://raybuck.com/common-issues-wi...2013-gm-trucks

Battery tested good, but I am going to get the alternator tested to make sure it’* still good.

You must have bought a good battery if it'* still holding at 4 years old.

the alternator had a bad diode sending ac current through the system

Ya nothing like a bad alt /diode to cause issues.. Is everything ok now?

Were the lights oscillating? That'* a sure sign of AC ripple.

It runs perfectly now