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:
Driving with a Trailer
Towing a trailer requires experience. Get familiar with handling and braking
with the added trailer weight. The vehicle is now longer and not as responsive as
the vehicle is by itself.
Check all ...
Hoses
Hoses transport fluids and should be regularly inspected to ensure that there are no cracks or leaks.
With a multi-point inspection, your dealer can inspect the hoses and advise if replacement is nee ...
Using the “Delete All Name Tags” Command
This command deletes all stored name tags in the Hands-Free Calling Directory and the OnStar Turn-by-Turn Destinations Directory, if equipped.
To delete all name tags:
1. Press and hold for two sec ...