2011 Toyota Sienna Owners Manual - Page 196
2011 Toyota Sienna Manual
Page 196 highlights
1-3. Adjustable components (seats, mirrors, steering wheel) STEP 2 Lower the seat and engage the latches. If you locked the seat latches unintentionally before installing securely, pull the release lever to unlock the latches. Make sure the seat is locked in place by trying to shake the seatback and lift up the seat cushion.