GMC 1999 Sierra 1500 Pickup Owner's Manual page 89

Automatic lLansmission
K2362
There are several different positions for your gear lever.
P (Park)
This locks your rear wheels. It's the best position to use when you start your
engine because your vehicle can't move easily.
*
It is dangerous to get out of your vehicle if the shift lever is not fully
in P (Park) 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, when you're on fairly level ground, always set your
parking brake and move the shift lever to P (Park).
If you have four-wheel drive, your vehicle will be free to roll-even
if
your shift lever is in P (ParkLif your transfer case is in N (Neutral).
So, be sure the transfer cas
s
in a drive gear-not N {"eutral).
See "Shifting Into P -
I;''
in tne 3 e x . If you are parking on a hill,
or
if you're pulling a traller, also see "Parking on Hills" or "Towing a
Trailer'' in the Index.
2-2 1