Toyota Prius Owner's Manual page 75

Back door (vehicles with entry function of front and back doors)
PRIUS_OM_OM47A19E_(EE)
1-3. Opening, closing and locking the doors
Press the unlock button to
unlock all the doors.
The doors cannot be unlocked for
3 seconds after the doors are
locked.
Press the lock button to lock all
the doors.
Check to see that all the side
doors and back door are securely
locked.
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