Toyota 2009 Yaris Hatchback Owner's Manual page 91

Items to check before locking the vehicle
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To prevent unexpected triggering of the alarm and vehicle theft, make sure
of the following.
Nobody is in the vehicle.
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The windows are closed before the alarm is set.
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l No valuables or other personal items are left in the vehicle.
Triggering of the alarm
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The alarm may be triggered in the following situations.
(Stopping the alarm deactivates the system.)
A person inside the vehicle opens a door or hood.
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1-6. Theft deterrent system
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