Hummer H2 2010 Owner's Manual page 156

The transfer case is a part of the Full-Time Four-Wheel
Drive system and allows the following four different
modes of operation:
4 (Full-Time Four-Wheel Drive): This setting is used
for driving in most street and highway situations. It can
be used for light or variable off-road conditions.
4 (Four-Wheel-High Lock): Use this mode when
you need extra traction in most off-road situations such
as sand, mud, snow, or level, rocky trails.
4 (Four-Wheel-Low Lock): This mode delivers
extra torque to all four wheels and is used for extreme
off-road conditions. Choose Four-Wheel-Low Lock while
driving off-road in deep sand, mud, or snow and
climbing or descending steep hills.
When in this mode you can also choose to lock the rear
axle for additional traction in extreme off-road situations.
See Locking Rear Axle on page 5 9.
Notice: Operating the vehicle in
Four-Wheel-Low Lock above 50 mph (80 km/h) for
any extended period of time could cause damage to
the transfer case. Do not operate the vehicle in
Four-Wheel-Low Lock above 50 mph (80 km/h) for
extended periods.
3-38
WARNING:
Shifting the transfer case to N (Neutral) can cause
the vehicle to roll even if the transmission is in
P (Park). You or someone else could be seriously
injured. Be sure to set the parking brake before
placing the transfer case in N (Neutral). See
Parking Brake on page 3 41.
N (Neutral): Shift the transfer case to N (Neutral) only
when towing the vehicle. See Recreational Vehicle
Towing on page 5 46 or Towing Your Vehicle on
page 5 46 for more information.
Indicator lights in the dial show which mode you are 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, take the vehicle to your dealer for service. An
indicator light will flash while shifting the transfer case.
It will remain on when the shift is complete. If the
transfer case cannot make a requested shift, it will
return to the last chosen setting.
If the SERVICE 4WD message stays on, you should
take the vehicle to your dealer for service. See Service
4WD message under Driver Information Center (DIC)
on page 4 42.