The back door can be locked/unlocked and opened/closed by the following procedures.
Locking and unlocking the back door
Opening/closing the back door from inside the vehicle (vehicles with a power back door)
Press and hold the switch to open or close, when the power back door is unlocked. (A buzzer sounds.)
Pressing the switch while the back
door is opening/closing stops the
operation. 
Side doors
Opening the back door from outside the vehicleHow to proceed with troubleshooting
Hint:
Use the procedure to troubleshoot the power door lock
control system.
*: Use the intelligent tester.
Vehicle brought to workshop
Inspect battery voltage
Standard voltage:
11 to 14 v
If the voltage is below 11 v, recharge or replace the battery
before proceeding.
...
If a warning light turns on or
a warning buzzer sounds
Calmly perform the following actions if any of the warning
lights comes on or flashes. If a light comes on or flashes, but
then goes off, this does not necessarily indicate a malfunction
in the system. However, if this continues to occur, have
the vehicle inspected by your Toyota dealer.
Actions to ...
On-vehicle inspection
Check fan and generator v belt
Visually check the drive belt for excessive wear,
frayed cords, etc.
If any defect has been found, replace the drive belt.
Hint:
Cracks on the rib side of a drive belt are considered
acceptable.
If the drive belt has chunks missing from the r ...