GMC 2013 Sierra Denali Owner's Manual page 276

Vehicles with a locking rear axle can
give more traction on snow, mud,
ice, sand, or gravel. It works like a
standard axle most of the time, but
when traction is low, this feature will
allow the rear wheel with the most
traction to move the vehicle.
Cruise control can be dangerous
where you cannot drive safely at
a steady speed. So, do not use
the cruise control on winding
roads or in heavy traffic.
Cruise control can be dangerous
on slippery roads. On such roads,
fast changes in tire traction can
cause excessive wheel slip, and
you could lose control. Do not use
cruise control on slippery roads.
With cruise control, a speed of
about 40 km/h (25 mph) or more can
be maintained without keeping your
foot on the accelerator. Cruise
control does not work at speeds
below about 40 km/h (25 mph).
When the brakes are applied, the
cruise control turns off.
If your vehicle has the StabiliTrak
system and begins to limit wheel
spin while you are using cruise
control, the cruise control will
automatically disengage. See
When road conditions allow the
cruise control to be safely used
again, it can be turned back on.
Press to turn the
system on or off. The indicator light
is on when cruise control is on and
turns off when cruise control is off.
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