The vehicle must be on a level surface when checking the coolant level.
It is normal to see coolant moving in the upper coolant hose return line when the engine is running.
Check to see if coolant is visible in the coolant surge tank. If the coolant inside the coolant surge tank is boiling, do not do anything else until it cools down.

If coolant is visible but the coolant level is not at or above the mark pointed to, add a 50/50 mixture of clean drinkable water and DEX-COOL coolant.
Be sure the cooling system is cool before this is done.
What to Use
How to Add Coolant to the Coolant Surge TankInsuring the Vehicle
Protect your investment in the GM vehicle with comprehensive and collision insurance
coverage. There are significant differences in the quality of coverage afforded
by various insurance policy terms.
Many insurance policies provide reduced protection to the GM vehicle by limiting
compensation ...
Driver Assistance Systems
Rear Vision Camera (RVC)
If equipped, the RVC system can assist the driver when backing up by displaying
a view of the area behind the vehicle.
Warning
The camera(s) do not display children, pedestrians, bicyclists,
crossing traffic, animals, or any other object outside of the cameras’ field ...
Lockout Protection
When locking is requested with the driver door open and the key in the ignition,
all the doors will lock and then the driver door will unlock. This can be manually
overridden by pressing and holding
on the power door lock switch.
If Unlocked Door Anti-Lockout is turned on, the vehicle is off ...