Lexus GS300 1998 Owner's Manual page 272

STARTING AND DRIVING
31G002
"LOCK" – Engine is off and the steering wheel is locked.
The ignition key can be removed only at this position.
To turn the key from "ACC" to the "LOCK" position, you
must put the transmission selector lever in the "P" position.
Once you remove the key, the engine immobiliser system is
automatically set. See "Engine immobiliser system" on page
14.
When starting the engine, the key may seem stuck at the
"LOCK" position. To free it, first be sure the key is pushed
all the way in, and then rock the steering wheel slightly while
turning the key gently.
If, in an emergency, you must turn the engine off while the
vehicle is moving, turn the key only to "ACC".
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