GMC 2011 Sierra Owner's Manual page 419

Add-on equipment can drain the
vehicle battery, even if the vehicle
is not operating.
The vehicle has an airbag system.
Before attempting to add anything
electrical to the vehicle, see
and
.
Before installing a snow plow on the
vehicle, here are some things you
need to know:
Some vehicles are built with a
special snow plow prep package,
called RPO VYU. If your vehicle
has this option, you can add a
plow to it, provided certain weights,
such as the weights on the vehicle's
axles and the Gross Vehicle
Weight (GVW), are not exceeded.
The plow the vehicle can carry
depends on many things, such as:
The options the vehicle came
with, and the weight of those
options.
The weight and number of
passengers you intend to carry.
The weight of items added to
the vehicle, like a tool box or
truck cap.
The total weight of any
additional cargo you intend
to carry.