GMC Yukon Denalid Owner's Manual page 142

If the ignition key is turned to the START, and
then released when the engine begins cranking,
the engine will continue cranking until the
vehicle starts or until it exceeds the maximum
cranking time allowed, approximately
15 seconds to prevent cranking motor damage.
To prevent gear damage, this system also
prevents cranking if the engine is already
running. The engine cranking can be stopped
by turning the ignition switch to the
ACCESSORY or LOCK.
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. Waiting about
15 seconds between each try, to allow
the cranking motor to cool down, will prevent
damage due to overheating.
2. If the engine does not start within 10 seconds,
push the accelerator pedal all the way to the
floor, while you hold the ignition key in
START. When the engine starts, let go of the
key and let up on the accelerator pedal.
Wait about 15 seconds between each try.
142
When starting your engine in very cold weather
(below 0°F or −18°C), do this:
1. With your foot off the accelerator pedal, turn
the ignition key to START and hold it there up
to 15 seconds. When the engine starts, let
go of the key.
2. If your engine still will not start, or starts but
then stops, it could be flooded with too much
gasoline. Try pushing your accelerator
pedal all the way to the floor and holding it
there as you hold the key in START for about
three seconds. When the engine starts, let
go of the key and accelerator. If the vehicle
starts briefly but then stops again, do the
same thing, but this time keep the pedal down
for five or six seconds. This clears the extra
gasoline from the engine.
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.