Lexus GS300 1998 Owner's Manual page 201

THEFT DETERRENT
Setting the system
1. Turn the ignition key to the "LOCK" position and
remove it.
The indicator light flashes by means of the engine
immobiliser system.
2. Close and lock all the doors, trunk and hood using an
ignition key or wireless remote control.
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If you lock them with wireless remote control, the turn signals
flash once.*
NOTE: *The turn signals can be set not to flash. Ask your
Lexus dealer for details.
The flashing indicator light will change to stay on when all the
doors, trunk and hood are closed and locked.
3. After 30 seconds, the indicator starts flashing and the
system is set.
Cancelling the system
When you unlock any door or trunk using an ignition key
or wireless remote control, the system is cancelled.
If you unlock any door or trunk with wireless remote control,
the turn signals flash twice.*
NOTE: *The turn signals can be set not to flash. Ask your
Lexus dealer for details.
Activating the system
The alarm sounds for 60 seconds if any of the following are
operated:
D Unlocking any door or trunk without using an ignition key
or wireless remote control.
D Opening the hood forcibly.
D Reconnecting the battery.