GMC Yukon XL Denali Owner's Manual page 397

WARNING
Batteries can hurt you. They can
be dangerous because:
They contain acid that can
burn you.
They contain gas that can
explode or ignite.
They contain enough
electricity to burn you.
If you do not follow these steps
exactly, some or all of these
things can hurt you.
Notice: Ignoring these steps
could result in costly damage to
the vehicle that would not be
covered by the warranty.
Trying to start the vehicle by
pushing or pulling it will not
work, and it could damage the
vehicle.
1. Check the other vehicle. It must
have a 12-volt battery with a
negative ground system.
Notice: Only use a vehicle that
has a 12-volt system with a
negative ground for jump
starting. If the other vehicle does
not have a 12-volt system with a
negative ground, both vehicles
can be damaged.
2. Get the vehicles close enough
so the jumper cables can reach,
but be sure the vehicles are not
touching each other. If they are,
it could cause a ground
connection you do not want. You
would not be able to start your
vehicle, and the bad grounding
could damage the electrical
systems.
Vehicle Care
To avoid the possibility of the
vehicles rolling, set the parking
brake firmly on both vehicles
involved in the jump start
procedure. Put the automatic
transmission in P (Park) or a
manual transmission in Neutral
before setting the parking brake.
Notice: If any accessories are left
on or plugged in during the jump
starting procedure, they could be
damaged. The repairs would not
be covered by the vehicle
warranty. Whenever possible,
turn off or unplug all accessories
on either vehicle when jump
starting the vehicle.
3. Turn off the ignition on both
vehicles. Unplug unnecessary
accessories plugged into the
accessory power outlets. Turn
off the radio and all the lamps
that are not needed. This avoids
sparks and helps save both
batteries. And it could save the
radio!
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