GMC 2013 Sierra Denali Owner's Manual page 265

Press the button located on the end
of the shift lever to turn Tow/Haul on
or off. While Tow/Haul is on, a light
on the instrument panel cluster
comes on.
See
and
for more
information.
Also see Tow Haul Mode under
more information.
Tow/Haul Mode Grade Braking is
only enabled while the Tow/Haul
Mode is selected and the vehicle is
not in the Range Selection Mode.
See Tow/Haul Mode listed
previously and
. Tow/Haul Mode Grade
Braking assists in maintaining
desired vehicle speeds when driving
on downhill grades by using the
engine and transmission to slow the
vehicle.
On vehicles with a gasoline engine,
to disable or enable Tow/Haul
Grade Braking within the current
ignition key cycle, press and hold
the Tow/Haul button for
three seconds. A DIC message will
be displayed. See
for
On vehicles with a diesel engine.
Tow/Haul Mode Grade Braking can
be enabled or disabled by pressing
the Tow/Haul Mode button. Use the
exhaust brake and Tow/Haul Mode
for maximum grade braking.
See
for more information.
For information on other forms of
grade braking, see
If the vehicle has this feature,
engine power is sent to all four
wheels when extra traction is
needed. This is like four-wheel
drive, but there is no separate lever
or switch to engage or disengage
the front axle. It is fully automatic,
.
and adjusts itself as needed for road
conditions.
If the vehicle has Four-Wheel Drive,
you can send the engine's driving
power to all four wheels for extra
traction. To get the most satisfaction
out of Four-Wheel Drive, you must
be familiar with its operation.
Read the following before using
and
Four-Wheel Drive.
.