GMC 2004 Sierra 1500 Pickup Owner's Manual page 135

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CAUTION:
Shifting the transfer case to NEUTRAL can
cause your vehicle to roll even if the
transmission is in PARK (P). You or someone
else could be seriously injured. Be sure to set
the parking brake before placing the transfer
case in NEUTRAL. See Parking Brake on
page 2-48 .
NEUTRAL: Shift the vehicle's transfer case to
NEUTRAL only when towing your vehicle. See
Recreational Vehicle Towing on page 4-54 or Towing
Your Vehicle on page 4-53 for more information.
Indicator lights in the switches show which setting your
transfer case is in. The indicator lights will come on
briefly when you turn on the ignition and one will stay on.
If the lights do not come on, you should take your
vehicle to your dealer for service. An indicator light will
flash while the transfer case is being shifted. It will
remain illuminated when the shift is complete. If
for some reason the transfer case cannot make a
requested shift, it will return to the last chosen setting.
If the SERVICE 4WD light stays on, you should take
your vehicle to your dealer for service. See Service on
page 5-3 for further information.
Shifting into 4HI or AUTO 4WD
Press and release the 4HI or AUTO 4WD switch. This
can be done at any speed (except when shifting
from 4LO), and the indicator light will flash while shifting.
It will remain illuminated when the shift is completed.
Shifting into 2HI
Press and release the 2HI switch. This can be done at
any speed (except when shifting from 4LO).
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