GMC Yukon Denali 2003 Owner's Manual page 289

Tow/Haul Mode
The tow/haul feature assists when pulling a heavy trailer
or a large or heavy load. The purpose of the tow/haul
mode is to:
•
Reduce the frequency and improve the predictability
of transmission shifts when pulling a heavy trailer or
a large or heavy load.
•
Provide the same solid shift feel when pulling a
heavy trailer or a large or heavy load as when
the vehicle is unloaded.
•
Improve control of vehicle speed while requiring
less throttle pedal activity when pulling a heavy
trailer or a large or heavy load.
Your vehicle is provided with a button at the end of the
shift lever which when pressed enables tow/haul.
When the button is pressed, a light on the instrument
panel will illuminate to indicate that tow/haul has
been selected. Tow/haul may be turned off by pressing
the button again, at which time the indicator light on
the instrument panel will turn off. The vehicle will
automatically turn off tow/haul every time it is started.
Tow/haul is designed to be most effective when the
vehicle and trailer combined weight is at least 75 percent
of the vehicle's Gross Combination Weight Rating
(GCWR). See Weight of the Trailer later in this section.
Tow/haul is most useful under the following driving
conditions:
•
When pulling a heavy trailer or a large or heavy
load through rolling terrain.
•
When pulling a heavy trailer or a large or heavy
load in stop and go traffic.
•
When pulling a heavy trailer or a large or heavy
load in busy parking lots where improved low
speed control of the vehicle is desired.
Operating the vehicle in tow/haul when lightly loaded or
with no trailer at all will not cause damage. However,
there is no benefit to the selection of tow/haul when the
vehicle is unloaded. Such a selection when unloaded
may result in unpleasant engine and transmission driving
characteristics and reduced fuel economy. Tow/haul
is recommended only when pulling a heavy trailer or a
large or heavy load.
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