GMC SIERRA 2002 Manual page 294

Tow/Haul Mode (If Equipped)
Tow/haul is a feature on automatic transmission
equipped vehicles that assists when pulling a heavy
trailer or a large or heavy load. The purpose of the
tow/haul mode is to:
D
Reduce the frequency and improve the predictability
of transmission shifts when pulling a heavy trailer or
a large or heavy load.
D
Provide the same solid shift feel when pulling a
heavy trailer or a large or heavy load as when the
vehicle is unloaded.
D
Improve control of vehicle speed while requiring less
throttle pedal activity when pulling a heavy trailer or
a large or heavy load.
Automatic transmission equipped vehicles are 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% of
the vehicle's Gross Combined Weight Rating (GCWR).
See "Weight of the Trailer" later in the section.
Tow/haul is most useful under the following
driving conditions:
D
When pulling a heavy trailer or a large or heavy load
through rolling terrain.
D
When pulling a heavy trailer or a large or heavy load
in stop and go traffic.
D
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.
4-65