GMC SIERRA 2002 Manual page 138

4WS: In this mode all four wheels will help steer the
vehicle. If you want to use 4WS, and your vehicle is not
in this mode, press the 4 Wheel Steer button, until the
4WS indicator, located to the right of the 4 Wheel Steer
button, lights up. If the 4WS indicator is flashing you
will have to center the steering wheel by turning it to the
left or right.
Slower Speed (below 40 m.p.h.)
At slower speeds the front and rear wheels will turn in
opposite directions. This helps the vehicle make tighter
turns, such as during parking, cornering and turning into
tight spaces.
Higher Speeds (40 m.p.h. and above)
At higher speeds the front and rear wheels will turn in
the same direction. This improves stability of the vehicle
during lane changes and sweeping turns.
4WS TOW: The 4WS TOW mode provides enhanced
stability allowing the trailer to follow the path of the tow
vehicle more closely, especially during lane changes.
In this mode the system operates much like the 4WS
mode, but is enhanced for trailer towing. It is
recommended for all types and weights of trailers.
To engage the 4WS TOW mode, press the 4 Wheel Steer
button until the 4WS and TOW indicators light up on
the instrument panel. If the TOW indicator is flashing
you will have to center the steering wheel by turning it
to the left or right. While in the 4WS TOW mode, it is
possible the steering wheel may be slightly off center.
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