I have a few cars and yes, I do have nice OBD2 reader, just saying. The dealership is not going to go by what you tell them the diagnostic code is. If anyone is afraid to spend a couple of hundred bucks to have it scanned and therefore placing the responsibility on the dealership, well, your money your choice.
It's so stupid that the car can't just tell you the codes/problem on one its screens. I was watching Vice Grip Garage revive an old V8-6-4 Caddy and he just pressed a couple of buttons on the HVAC pad to make the codes read out on the display.