Unable to Connect to OnStar Message
If there is limited cellular coverage or the cellular network has reached maximum capacity, this message may come on. Push 
to try the call again or try again after driving a few miles into another cellular area.
See also:
Transportation Options
Warranty service can generally be completed while you wait. However, if you are unable to wait, GM helps to minimize inconvenience by providing several transportation options. Depending on the circums ...
After Off-Road Driving
Remove any brush or debris that has collected on the underbody or chassis, or under the hood. These accumulations can be a fire hazard.
After operation in mud or sand, have the brake linings cleaned ...
How to Check
Use a good quality pocket-type gauge to check tire pressure.
Proper tire inflation cannot be determined by looking at the tire.
Check the tire inflation pressure when the tires are cold, meaning the ...