1. Check the fuse. The power door may not be working due to a blown fuse. Check the fuse box for a blown fuse labeled "Power Door" or something similar. If the fuse is blown, replace it with a new fuse of the same amperage.
2. Check the door switch. The door switch may be faulty, which is preventing the power door from opening. To check the door switch, press the button to open the door. If the door does not open, the switch may be defective and will need to be replaced.
3. Check the door lock actuator. The door lock actuator may be faulty, which is preventing the power door from opening or closing. To check the door lock actuator, try manually unlocking and locking the door using the key. If the door does not unlock or lock, the actuator may be defective and will need to be replaced.
4. Check the wiring. The wiring for the power door may be damaged, which is preventing the door from working. Inspect the wiring for any cuts, breaks, or loose connections. If you find any damage to the wiring, it will need to be repaired or replaced.
5. Check the door motor. The door motor may be faulty, which is preventing the power door from opening or closing. To check the door motor, try manually opening or closing the door. If the door does not move, the motor may be defective and will need to be replaced.
If you are unable to identify and fix the problem yourself, you may need to take your Sienna to a mechanic for further diagnosis and repair.
