Trying to diagnose some sort of electrical problem. LR3 V8 runs fine and no issues starting, but for the past few weeks after longer highway drives (say 45 minutes plus) I am seeing the red battery light come on, the GAP tool reports the voltage is jumping around from 11.8-15.7V (doesn't seem to track RPM), and the radio will flicker (the actual audio output more than the display.)
The yellow brake light also comes on.
GAP tool shows P0622-00 (2A) Generator field terminal circuit error (with check engine light.)

The alternator seems to be charging the battery OK, no difficulty starting over the past few weeks, and when I check the battery with it running in the driveway I see 14.1V so it seems like it's charging at least some of the time.

I found several threads of similar issues but am hoping for a bit of guidance--sounds like pulling battery and checking for corrosion is in order?
Battery is an Interstate from 2020, so hoping it's not the culprit, but suppose it could be?

Thanks for any suggestions.

 

Replace alternator.