Lexus RX300 2003 Owner's Manual page 169

THEFT DETERRENT SYSTEM
17R013
To deter theft of the vehicle, this system is designed to
sound an alarm if any of the doors or hood is forcibly
unlocked or the battery terminal is disconnected and then
reconnected while the vehicle is locked.
The alarm blows the horn intermittently and flashes the
headlights, tail lights and other exterior lights.
17R014
" Security indicator light
Setting the system
1. Turn the ignition key to the "LOCK" position and
remove it.
The engine immobiliser system causes the indicator light to
flash.
2. Close and lock all the doors and hood using an ignition
key or wireless remote control.
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 remain on when all the doors
and hood are closed and locked.
3. After 30 seconds, the indicator starts flashing and the
system is set.