GMC 2007 Yukon Denali Owner's Manual page 142

If the ignition key is turned to the START
position, and then released when the engine
begins cranking, the engine will continue
cranking for a few seconds or until the vehicle
starts. If the engine does not start and the key
is held in START for many seconds, cranking
will be stopped after 15 seconds to prevent
cranking motor damage. To prevent gear
damage, this system also prevents cranking if
the engine is already running. Engine cranking
can be stopped by turning the ignition switch to
the ACCESSORY or LOCK position.
Notice: Cranking the engine for long periods
of time, by returning the key to the START
position immediately after cranking has ended,
can overheat and damage the cranking
motor, and drain the battery. Wait at least
15 seconds between each try, to allow
the cranking motor to cool down.
142
2. If the engine does not start after 5-10 seconds,
especially in very cold weather (below 0°F
or −18°C), it could be flooded with too much
gasoline. Try pushing the accelerator pedal
all the way to the floor and holding it there
as you hold the key in START for up to
a maximum of 15 seconds. Wait at least
15 seconds between each try, to allow
the cranking motor to cool down. When the
engine starts, let go of the key and
accelerator. If the vehicle starts briefly but
then stops again, do the same thing.
This clears the extra gasoline from the
engine. Do not race the engine immediately
after starting it. Operate the engine and
transmission gently until the oil warms up and
lubricates all moving parts.
Notice: Your engine is designed to work with
the electronics in your vehicle. If you add
electrical parts or accessories, you could
change the way the engine operates. Before
adding electrical equipment, check with your
dealer. If you do not, your engine might not
perform properly. Any resulting damage would
not be covered by your vehicle's warranty.