GMC SIERRA DENALI 2002 Manual page 93

There are several different positions for your shift lever.
PARK (P): This position locks your rear wheels. It's the
best position to use when you start your engine because
your vehicle can't move easily.
CAUTION:
It is dangerous to get out of your vehicle if the
shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
Don't leave your vehicle when the engine is
running unless you have to. If you have left the
engine running, the vehicle can move suddenly.
You or others could be injured. To be sure your
vehicle won't move, even when you're on fairly
level ground, always set your parking brake and
move the shift lever to PARK (P).
See "Shifting Into PARK (P)" in the Index.
If you're pulling a trailer, see "Towing a Trailer"
in the Index.
2-20
REVERSE (R): Use this gear to back up.
NOTICE:
Shifting to REVERSE (R) while your vehicle is
moving forward could damage your transmission.
Shift to REVERSE (R) only after your vehicle
is stopped.
To rock your vehicle back and forth to get out of
snow, ice or sand without damaging your transmission,
see "Stuck: In Sand, Mud, Ice or Snow" in the Index.
NEUTRAL (N): In this position, your engine
doesn't connect with the wheels. To restart when you're
already moving, use NEUTRAL (N) only. Also, use
NEUTRAL (N) when your vehicle is being towed.