Parental Control
The RSE system may have a Parental Control feature, depending on the radio. To enable Parental Control, press and hold the radio power button for more than two seconds to stop all system features such as: radio, video screen, RSA, DVD and/or CD.
While Parental Control is on, 
displays.
When the radio is turned back on, Parental Control is unlocked.
See also:
Instrument Panel Illumination Control
This control is located on the instrument panel, to the left of the steering
column.
(Instrument Panel Brightness): Turn
clockwise or counterclockwise to brighten or dim the lights. ...
Interior details and flexibility
The GMC Terrain's rich, premium interior is influenced by industrial
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Cleaning the Mirror
Do not spray glass cleaner directly on the mirror. Use a soft towel dampened
with water. ...