Lexus GS300 1998 Owner's Manual page 200

THEFT DETERRENT SYSTEM
To deter theft of the vehicle, this system is designed to give
an alarm if any of the doors, trunk or hood is forcibly
unlocked or the battery terminal is disconnected and then
reconnected while the vehicle is locked.*
NOTE: *The system operating condition can be changed.
Ask your Lexus dealer for details.
The alarm blows the horn intermittently and flashes the
headlights, tail lights and other exterior lights.
17G001
THEFT DETERRENT
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