2010 Toyota Sienna Owners Manual - Page 117

1-3. Adjustable components (seats, mirrors, steering wheel) Seat belt comfort guide (outer third seat) If the shoulder belt sits close to a person's neck, use the seat belt comfort guide. Seat belt pretensioners (front seats) The pretensioner helps the seat belt to quickly restrain the occupant by retracting the seat belt when the vehicle is subjected to certain types of severe frontal collision. The pretensioner may not activate in the event of a minor frontal impact, a side impact or a rear impact.