This was taken from http://www.findonefindall.com/toyota...structions.htm
PROGRAMMING THE DOOR REMOTE ON A TOYOTA SIENNA 2001
Start with your key is out of the ignition and driver door only open. Sit in van.
Make sure driver's door is unlocked
(Perform these steps within 40 seconds)
1) Stick key into the ignition (don't turn it) and then pull it out.
2) Push the power lock/unlock switch on the driver's door (with the door still open) through 5 lock/unlock cycles starting with lock.
(A lock/unlock cycle consists of pressing the power lock switch, followed by pressing the power unlock switch on the driver's door panel)
Don't dawdle, you only have 40 seconds to do all this).
3) Then close, then open, the driver's door.
4) Then do the 5 lock/unlock cycles again. (just repeat Step 2)
5)Now put your key back in and turn to ON (don't start the engine though) Just go as far as you can without starting it. Then back to OFF
6) Repeat step 5
7) Remove the key from ignition.
In 3 seconds, the power door locks should cycle on their own (lock then unlock) , indicating successful entry into programming mode.
If this does not happen, you must have missed something, so go back to Step 1
8) Press both the lock and unlock buttons on the transmitter (on the remote) simultaneously for about 1 second.
9) After letting go of the lock and unlock buttons, hit the lock button by itself and hold it for 2 seconds.
Within 3 seconds, the door locks should cycle (lock then unlock) once indicating successful programming. If the door locks don't cycle, or cycle twice, start over.
10. Close the driver's door. This ends the programming session.
You have to repeat steps 8 & 9 for EVERY remote, both your old ones that were already working, and your new one(s). And you have to do it before closing the driver's door in step 10.
Don't TEST the remotes until you have completed all the remotes
I do hope this helps.