GMC 2009 Sierra - Manual (Page 342)

The coolant level should be at or above the FULL COLD
mark. If it is not, you could have a leak at the pressure
cap or in the radiator hoses, heater hoses, radiator, water
pump, or somewhere else in the cooling system.
{ CAUTION:
Heater and radiator hoses, and other engine
parts, can be very hot. Do not touch them.
If you do, you can be burned.
Do not run the engine if there is a leak.
If you run the engine, it could lose all coolant.
That could cause an engine fire, and you
could be burned. Get any leak fixed before
you drive the vehicle.
Notice: Engine damage from running your engine
without coolant is not covered by your warranty. See
Overheated Engine Protection Operating Mode on
page 5-28 for information on driving to a safe place
in an emergency.
Notice: Using coolant other than DEX-COOL ® may
cause premature engine, heater core, or radiator
corrosion. In addition, the engine coolant could
require changing sooner, at 30,000 miles (50 000 km)
or 24 months, whichever occurs first. Any repairs
would not be covered by the warranty. Always
use DEX-COOL
® (silicate-free) coolant in the vehicle.
5-30