Hey everybody, so I just purchased a 2020 2500hd High Country about a month ago and the infamous B pillar vibration began two days ago. The rattling was very subtle at first and then progressively became very loud right next to my left ear. It became so annoying I couldn't even drive a mile without becoming pissed off with everything. So this afternoon I manned up and took off the interior trim on the B pillar and tried simulating vibrations from the road and everything was tight. I thought okay surely its the mechanism on the door rattling on the latch of the pillar. No Biscuit. I got on the floor outside my hotel and started messing with the side step. The clicking noise sounded when i "gently" hit the sidestep. However, after removing the sidestep and going on a test drive the Clicking noise was ever present. Just when i was about to give up i began tapping the B pillar from the stickers that read you trailer weights and load ranges all the way to the top of the roof. I noticed a very very slight rattle by the latch on pillar that meets the lock mechanism on the door. i began pulling and trying to move the metal latch and sure enough the clicking started. There must be a piece of sheet metal that is vibrating on the inside of the pillar. I grabbed a pry-bar and firmly started pulling the latch in the direction of the front of the truck alternating between under the latch and above the latch to ensure it stayed flat and trued. As soon as i stopped hearing the clicking noise i did this twice more to ensure the heat expansion would cause this again. I took it for a test drive 30mins ago and all is good. Now i just have to fix the reverse parking camera on the tailgate. It will randomly be black at times and then when driving it comes back on as if normal.
Hope this helps.