Your Responsibility
Increase the volume of the radio if the OnStar Advisor cannot be heard.
If the light next to the OnStar buttons is red, the system may not be functioning properly. Push 
and request a vehicle diagnostic check. If the light appears clear (no light appears), your OnStar subscription has expired and all services have been deactivated.
Push to confirm that the OnStar equipment is active.
See also:
How to Add Coolant to the CoolantRecovery Tank
If you have not found a problem yet, but the
coolant level is not at the FULL COLD mark, add
a 50/50 mixture of clean, drinkable water and
DEX-COOL® engine coolant at the coolant
recovery tank.
...
Lap-Shoulder Belt
All seating positions in the vehicle
have a lap-shoulder belt.
The following instructions explain
how to wear a lap-shoulder belt
properly.
1. Adjust the seat, if the seat is
adjustable, so ...
Adjusting the Volume
Turn the VOL/ knob to adjust the
volume of the infotainment system
after the volume level has been set
on the portable audio device. ...