The sliding door on my 2004 toyota sienna won't close

To turn off the door sensor on your 2004 Toyota Sienna, you will need to follow these steps:

1. Open the door of your Sienna and locate the door sensor, which is a small black or silver button located near the top of the door frame.
2. Press and hold the door sensor button for a few seconds until the sensor's light turns off.
3. Close the door and test the sensor to make sure it is no longer active.

Note: Disabling the door sensor will prevent your Sienna from automatically locking or unlocking the doors when you open or close them.

Is it locked

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.

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.

Here is a fix for a 1999 Sienna with a broken door cable.

If you can remove the inner door panel you will see a maze of cables running to the various locking points on the sliding door. If the cable going to the FRONT latch on the sliding door is broken (or in my case, simply dislodged inside the door) the door acts as if it is frozen shut.

The front cable is short, and easily replaced even by a newbie mechanic.

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 suggested fix above did fix my problem. The problem is that a 2.5" hinged finger that pops up from the floor of the door opening to block the door. Apparently, the finger should, but doesnt go back down after the gas flap is closed. Even after I got hinged finger down (so that the sliding door would open/close all the way), it still would not go back down after the gas flap has been opened. i.e. I have to push the finger back down every time after we fill up with gas. It looks like there is a little wire/spring that should pull the finger back down, but it is off of the finger. I think that replacing this back on the finger should fix the problem permanently.

iv had a few people come in with that complaint I clean inside of door and spray seal with good 100% silicone spray and spray latches with penetrating oil

Sounds like something isn't right.Try to disconnect the battery for a few minutes and see if that helps.Some times the ecu gets haywired and disconnecting the battery might reset it.And if it is the original battery you might want to get it tested.