GMC 1996 Sierra Owner's Manual page 90

Leaving
Your
Vehicle With the Engine
Running (Automatic Transmission
Models Only)
I A
'CAUTION:
It can be dangerous to leave your vehicle with the
engine running. Your vehicle could move suddenly
if the shift lever is not fully in PARK (P) with the
parking brake firmly set. If you have four-wheel
drive with a manual transfer case shift lever and
your transfer case is in NEUTRAL (N), your
vehicle will be free to roll, even if your shift lever
is in PARK
(P).
So be sure the transfer case is in a
drive gear
--
not in NEUTRAL (N). And, if you
leave the vehicle with the engine running, it could
overheat and even catch fire. You or others could
be injured. Don't leave your vehicle with the
engine running unless you have to.
If you have to leave your vehicle with the engine
running, be sure your vehicle is in PARK (P) and the
parking brake is firmly set before you leave it. After you
move the shift lever into PARK (P), hold the regular
brake pedal down. Then, see if you can move the shift
lever away from PARK (P) without first pulling it
toward you. If you can, it means that the shift lever
wasn't fully locked into PARK (P).
Torque Lock (Automatic Transmission)
If you are parking on
a
hill and you don't shift your
transmission into PARK (P) properly, the weight of
the vehicle may put too much force on the parking
pawl in the transmission. You may find it difficult to
pull the shift lever out of PARK (P). This is called
"torque lock." To prevent torque lock, set the parking
brake and then shift into PARK (P) properly before you
leave the driver's seat. To find out how, see "Shifting
Into PARK (P)" in the Index.
When you are ready to drive, move the shift lever out of
PARK (P) before you release the parking brake.
If torque lock does occur, you may need to have another
vehicle push yours a little uphill to take some of the
pressure from the transmission, so you can puIl the shift
lever out of PARK (P).
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