GMC 2003 Yukon Owner's Manual page 299

The switch is located on the instrument panel.
2: In this mode the vehicle will operate like any other
vehicle with two wheel steering. If you want to use
2 wheel steer mode and your vehicle is not in this mode,
press the button until the 2 indicator, located to the
right of the 4 Wheel Steer button, lights up. If the
2 indicator is flashing you will have to center the steering
wheel by turning it to the left or right.
Your vehicle will return to 2 when the transmission is
shifted into NEUTRAL, for example when entering a
car wash.
If you want to use tire chains, the vehicle needs to be in
2 wheel steer mode. For more information see Tire
Chains on page 5-68 .
4: In this mode all four wheels will help steer the
vehicle. If you want to use 4, and your vehicle is not in
this mode, press the button, until the 4 indicator,
located to the right of the 4 Wheel Steer button, comes
on and stays on. If the 4 indicator is flashing you will
have to center the steering wheel by turning it to the left
or right.
Slower Speeds (below 40 m.p.h./ 64 km/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.
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