I had the same issue with my passenger side mirror not working on my 2014 Silverado. Turned out to be broken wired in the drivers door jamb inside the rubber boot. The door harness is not available new, so I repaired the wires. Everything works perfect. Once you take the door panel off and remove the speaker, you can disconnect the wires at the cab side of the jamb and pull them through the door. Gives you alot more room then trying to repair them in the jamb. I had 4 or 5 broken wires. The job isn't as bad as it sounds, just tedious. I soldered the wires and used heat shrink. Also check the other wires for insulation cracking. I would start with the drivers door becaude it get used more.