Toyota 2012 Highlander Owner's Manual page 266

3-1. Using the air conditioning system and defogger
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The defogger can be operated when
Vehicles without smart key system
The engine switch is in the "ON" position.
Vehicles with smart key system
The "ENGINE START STOP" switch is in IGNITION ON mode.
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Outside rear view mirror defoggers (vehicles with outside rear view
mirror defoggers)
Turning the rear window defogger on will turn the outside rear view mirror
defoggers on.
CAUTION
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Outside rear view mirror defoggers (vehicles with outside rear view
mirror defoggers)
Do not touch the outside surface of the rear view mirrors, as they can
become very hot and cause burns.
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