GMC Hummer H3 2008 Owner's Handbook Manual page 195

Starting and Operating Instructions
CAUTION
Make sure that the transfer case
is in a drive gear and not in N
(Neutral). Otherwise, the vehi-
cle will be free to roll even if the
shift lever is in P (Park).
Leaving the ignition on for an
extended period of time will flat-
ten the battery because the shift
position display will be on when-
ever the transmission is not locked.
If you must leave your key in the
ignition for an extended period of
time and it is not in the LOCK posi-
tion, disconnect the battery cable
to prevent discharge.
. . . 194
There are several different shift
positions for your gear lever.
P (Park)
This locks your rear wheels. Use
this position to park the vehicle
and when starting the engine.
Your vehicle has an automatic
transmission shift lock control
system. With the ignition on, you
have to fully apply the regular
brakes and press the shift lever
button before you can shift out of
P (Park).
See "Shift Lock Control System"
later in this section for more
information.
CAUTION
When you leave your vehicle,
be sure the shift lever is fully in
P (Park) and the park brake is
firmly applied.
Do not leave your vehicle while
the engine is running.
Make sure that the transfer case
is in a drive gear and not in N
(Neutral). Otherwise, the vehi-
cle will be free to roll even if the
shift lever is in P (Park).
See "Vehicle Parking" later in this
section for more information.