2022 GMC Terrain SLT, rear driver side turn signal stopped working, then rear backup light assembly stopped working, then the full tail/brake light assembly stopped working. Service shop tried reprogramming BCM and that did not work. Has anyone had this problem? There is no power going to the rear driver side of the vehicle. Any help would be greatly appreciated.

Shop can program but don';t know how to test a simple circuit. Probably a splice going to the rear.

I will have husband do some searching and see if there is a faulty wire and let you know what I find out

It'* not something he'* likely to find unless he has knowledge of automotive electrical and a schematic.
A shop should be able to find it.

The shop probably should have tested the circuits before reprogramming the BCM to fix the issue.

LOL, you'd be surprised.

Had a 2021 Volvo truck come in and the wipers only worked when you hit the washer fluid.
Updated the LCM(Light Control Module), now works as should.

Definitely. It is amazing how they are attaching some of the silliest things deeply to the code in the PCM. At the same time, in OP'* case a meter testing a socket would have been a better first test. Could have been a bad bulb or corroded socket for all we know.