This bulletin applies to 2009-2019 Chevy Suburban vehicles. A high-pitched whine or buzz noise may be heard with the key on and engine off, or for up to one minute after the engine has been shut off.
The noise can be heard from outside of the vehicle only, most noticed in an enclosed area.
The noise may be caused by the internal transmission solenoids being commanded to minimum line pressure by the TCM (transmission control module). The noise should be considered normal.