GMC Yukon 2007 Owner's Manual page 226

The accessory power outlets are powered, even
with the ignition off. Continuing to use power
outlets while the ignition is off may cause
the vehicle's battery to run down.
Notice: If electrical devices are left plugged
into a power outlet, the battery may drain
causing your vehicle not to start or damage to
the battery. This would not be covered by
the warranty. Always unplug all electrical
devices when turning off your vehicle.
Certain power accessory plugs may not be
compatible to the accessory power outlet and could
result in blown adapter or vehicle fuses. If you
experience a problem, see your dealer for
additional information on the accessory
power plugs.
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Notice: Adding any electrical equipment to
your vehicle may damage it or keep other
components from working as they should. The
repairs would not be covered by your
warranty. Do not use equipment exceeding
maximum amperage rating of 20 amperes.
Check with your dealer/retailer before adding
electrical equipment.
When adding electrical equipment, be sure to
follow the proper installation instructions included
with the equipment. Do not use equipment
exceeding the maximum amperage rating of
20 amperes.
Notice: Improper use of the power outlet can
cause damage not covered by your warranty.
Do not hang any type of accessory or
accessory bracket from the plug because the
power outlets are designed for accessory
power plugs only.