2001 Toyota Sienna r.h. sliding door ''rear latch switch'' location

Your question is too vague about the "problem". Is it alignment, latching, locking, handle, etc.? Try looking at the following links:
https://www.facebook.com/Toyota-Sienna-Faulty-Power-Sliding-Doors-233250320033754/
or http://www.siennachat.com/forum/66-problems-maintenance-repair/1300-sienna-power-sliding-door-problems-thread.html
hopefully you will find a solution there.

Can be issue with the switch.
Help links are provided below for detailed procedure,Click the link below:---
Front Door dis-assembly diagram for Toyota car?

http://repairhelpcenter.blogspot.in/2012/02/front-door-dis-assembly-diagram-for.html

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Rear Door dis-assembly diagram for Toyota car?

http://repairhelpcenter.blogspot.in/2012/02/rear-door-dis-assembly-diagram-for.html

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How to test Power door locks? http://repairhelpcenter.blogspot.in/2012/02/how-to-test-power-door-locks.html

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right side slide door light switch on Toyota Sienna? http://repairhelpcenter.blogspot.com/2012/01/details-for-replacing-right-side-slide.html

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Door locks not working? http://technoanswers.blogspot.com/2012/01/door-locks-not-working-on-ford-explorer.html

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Power door locks not working? http://schematicsdiagram.blogspot.com/2011/12/power-door-locks-not-working.html

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Repairing car Door lock Actuator?
http://howtobyme.blogspot.com/2011/11/repairing-car-door-lock-actuator.html

How to Access car door panel?
http://howtobyme.blogspot.com/2011/11/how-to-access-car-door-panel.html

Vehicle door panel components?
http://howtobyme.blogspot.com/2011/11/vehicle-door-panel-components.html

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This will help.
Thanks.

Remove the internal handle and I think 1 or 2 screws and lift inside door panel off, pull the latch and it will open!!

Try this... it fixed my problem whereby the 2005 Toyota Sienna passenger sliding door would sometimes open and sometimes not, yet I could hear the motor trying to open/close it. It cost me 20 minutes and 10 drops of oil, not $1200.

First, get the door open. It took me two weeks of constant trying, but it finally opened.

Next, remove the plastic covering of the inside door handle this way: locate the two screws on the forward edge of the sliding door near the child-safety switch: (the switch is a small lever near the door latch, on the forward edge of the door) loosen and remove the two phillips screws, one above the child-safety latch, and one below.

Remove the plastic cover to expose the gears for the door open/close mechanism.

There's a bunch of intricate plastic and metal parts in there, all coated with white grease. I used some 3-n-1 oil to lubricate everything in there thoroughly, In my case, there was one part that was a little void of grease, hence it "stuck" occasionally.

Test the system. If it's Okay, replace the plastic cover, and re-install the screws.

Now my Toyota Sienna 2005 door never fails to open or close.

I got this problem with my 2001 Sienna too.
The Toyota deal said the computer BD is bad.
They charge me about $350 to replace with a new one.
However, the new parts is in shortage.
They said lots of back order for it!

well they dont use cables they use a iron rod so just snap off the pannel the snaps are in the out side of the door then just remove the arm rest and the panel comes right off remove the dirt cover then just tighen it and it will work again

This may or may not work depending on exactly what is wrong with the door, I cant tell what is wrong without looking at it directly however:
You can try starting with all doors closed and unlocked, keys in hand disconnecting the battery and letting the vehicle sit for 2 min or so, then reconnect the battery. Put the key into the ignition and turn it to the on position but do not start the van. Next press the button to disable the power sliding door for the drivers side, then manually open the door fully, wait 5 seconds, then close it manually fully. Press button the button again to re-enable the power sliding door, then try to use it with the automatic feature either by pulling the handle or using your remote, this may or may not work depending on if the door has somehow become de-initialized (it should work now) however if something is broken inside the door closing mechanism or door closed/open sensors, the door will continue to malfunction.

Hold the door handle in the open position while using a bent coat hanger on the door catch lever.Sometimes a flathead screwdriver works to pry the door catch as well. Good luck, keep me posted.

there is a door lock actuator that has failed, it releases the latches so the door can open. you need to remove the door panel. unbolt the window and tape it as to hold the window up then remove the window regulator assembley then unbolt the lock actuator from the back side.

the sienna has a latch type which is interferring the door use a screw driver and tap it down then the door will slide then next oil change have them lube it