GMC Sierra Owners Manual
Park Tilt Mirrors
If the vehicle has the memory package, the passenger and/or driver mirror tilts to a preselected position when the vehicle is in R (Reverse). This feature lets the driver view the curb when parallel parking. The mirror(s) return to the original position when the vehicle is shifted out of R (Reverse), or the ignition is turned off or to OFF/LOCK.
Turn this feature on or off through the Driver Information Center (DIC).
See Vehicle Personalization (With DIC Buttons) on page 5‑52 for more information.