Hi all, I just picked up a new 2018 GMC with the base radio with XM and Onstar option. I cannot get the screen illumination to dim even with the instrument panel dimmer switch. Can’t find any prompts on radio menus. I have searched owners manual for details, to no avail. Night driving, I have to turn radio off in order to safely drive. Thought I would start here to see if anyone else has noticed this before I head to dealer. Thanks!