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:
Trailer Sway Control (TSC)
The vehicle has a Trailer Sway Control (TSC) feature as part of the StabiliTrak
system. If TSC detects that the trailer is swaying, the vehicle's brakes are automatically
applied.
When TSC ...
Immobilizer
See Radio Frequency Statement on page 13‑22 for information regarding Part 15 of the Federal Communications Commission (FCC) rules and Industry Canada Standards RSS-GEN/210/220/310. ...