There does not appear to be any information on the internet on the warning light that you described, but I suspect that it may either indicate a problem with your Toyota's ignition, or it may merely warn the driver that a door on the vehicle, or the trunk, is not securely closed.
Could be a problem with your ignition switch.
Check your owners manual.
The warning light information is listed in the manual.
Check your owners manual.
The warning light information is listed in the manual.
Service department sez it is a signal that the Sienna is looking for a coded transponder ignition key to be inserted.
Appears it may be a signal to anyone hoping to steal car that a special coded transponder key is required so move on to another steal.
Appears it may be a signal to anyone hoping to steal car that a special coded transponder key is required so move on to another steal.