Hummer 2007 H2 Owner's Manual page 131

If the Four-Wheel-Low Lock button is pressed
when your vehicle is in gear and/or moving, the
Four-Wheel Low Lock indicator light will flash
for 15 seconds and not complete the shift unless
your vehicle is moving less than 3 mph (5 km/h)
and the transmission is in NEUTRAL (N).
After 15 seconds the transfer case will return to
the setting last chosen.
Shifting Out of Four-Wheel Low Lock
To shift from Four-Wheel-Low Lock to Four-Wheel
High or Four-Wheel-High Lock, your vehicle
must be stopped or moving less than 3 mph
(5 km/h) with the transmission in NEUTRAL (N)
and the ignition in RUN. The preferred method for
shifting out of Four-Wheel-Low Lock is to have
your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h).
Press and release the Four-Wheel High or
Four-Wheel-High Lock button. You must wait for
the Four-Wheel High or Four-Wheel-High Lock
indicator light to stop flashing and remain lit before
shifting your transmission into gear.
It is normal for your vehicle to have engagement
noise and bump when shifting between
Four-Wheel Low and Four-Wheel High or
Four-Wheel-High Lock ranges or from NEUTRAL
with the engine running.
If the Four-Wheel High or Four-Wheel-High Lock
button is pressed when your vehicle is in gear
and/or moving, the Four-Wheel High or
Four-Wheel-High Lock indicator light will flash for
30 seconds but will not complete the shift
unless your vehicle is moving less than 3 mph
(5 km/h) and the transmission is in NEUTRAL (N).
Notice: Shifting the transmission into gear
before the indicator light stops flashing could
cause damage to the transfer case. Always
wait until the indicator light stops flashing
before putting the transmission back in gear.
131