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:
Customer Assistance Offices (U.S. and Canada)
GMC encourages customers to call the toll-free number for assistance.
However, if a customer wishes to write or e-mail GMC, the letter should be addressed to:
United States
GMC Customer Assistance ...
If No Steam Is Coming from the Engine Compartment
If an engine overheat warning is displayed but no steam can be seen or heard, the problem may not be too serious. Sometimes the engine can get a little too hot when the vehicle:
• Climbs a long hil ...
Checking Coolant
The vehicle must be on a level surface when checking the coolant level.
Check to see if coolant is visible in the coolant surge tank. If the coolant
inside the coolant surge tank is boiling, do not ...