GMC 1999 Sierra 1500 Pickup Owner's Manual page 79

LOCK: This position locks your ignition, steering wheel and transmission. It's
a theft deterrent feature.
You
will only be able to remove your key when the
ignition is turned to LOCK.
Off: This position lets you turn off the engine but still turn the steering wheel.
Use Off if you must have your vehicle in motion while the engine is off (for
example, i f your vehicle is being pushed).
Run: This is the position for driving.
Start: This starts your engine.
A
On manual transmission vehicles, turning the key to LOCK will lock
I
A
the steering column and result in a loss of ability to steer the
vehicle. This could cause a collision. If you need to turn the engine
off while the vehicle is moving, turn the key only to OFF. Don't move
the key release lever while the vehicle is moving.
-
f your key seems stuck in LOCK and you can't turn it, be sure it is all
:he way in. If it is, then turn the steering wheel left and right while you
:urn the key hard. But turn the key only with your hand. Using a tool to
'orce it could break the key or the ignition switch. If none of this works,
:hen your vehicle needs service.
NOTICT
I
Key Release Levc-
KO495
The ignition k e y cannot be removed from the ignition of manual transmission
vehicles unless the key release lever is used.
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