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:
Door Locks
There are several ways to lock and unlock the vehicle.
From outside, use the Remote Keyless Entry (RKE) transmitter or the key in the driver door.
From inside, use the power door locks or the manual ...
Lamp Messages
TURN SIGNAL ON
This message displays and a chime sounds if a turn signal is left on for 1.2 km (0.75 mile). Move the turn signal/multifunction lever to the off position. ...
Engine Oil
For diesel engine vehicles, see “Engine Oil” in the Duramax Diesel Supplement.
To ensure proper engine performance and long life, careful attention must be paid to engine oil.
Following these si ...