So, after cursing the horn on numerous occasions, I finally broke down and decided to attempt the repair. You know, when I was younger working on vehicles was something that intrigued me, but now that I'm on the backside of 40, I no longer get the same sense of excitement and adventure as I once had--The feeling I get now is that sinking feeling in my stomach, thinking, "there are so many other things I would rather be doing than twisting wrenches." Yet, because of my frugality, stubbornness, and "I can fix it!" attitude, I dutifully enter the garage....
So I pulled the Haynes manual, found the wiring diagram, and went to work. I pulled the cover from fuse & relay box under the hood and checked the fuses: all were good - check. Then I pulled the horn relay and tested it using the battery: it clicked when energized - check. Next, with the relay still pulled from its socket, I ran a jumper across the receptacles in the relay socket and the horn blasted loudly - check.
This led me to believe the trouble was between the steering wheel horn pad switch and the relay. A Google search revealed that there is no wire that grounds the steering wheel to the frame, but that the steering wheel is grounded via bearings. According to online sources (i.e., discussion boards, see this link http://www.automotiveforums.com/t894269-sienna_2000__horn_works_only_when_car_is_not_moving.html) the grease lubricating the bearings dries over time, coating the bearings in dry lubricant, which acts as an insulator. This dry grease prevents the flow of electricity from the steering housing, through the bearings, to the steering wheel. To remedy this situation you just have to lubricate the bearings. Simple! But where are these mysterious bearings? Discussion boards stated they were near the top of the steering wheel, but no photos existed. So, to help other frugal weekend mechanics I am posting photos of the bearing location here. In fact, I'll post photos of the entire process. This took me about an hour to complete the entire process.
A few disclaimers before we get started....
Disclaimer #1: The information posted is for informational use only. Use it at your own risk as the statements on this page may be completely wrong, or your vehicle may not be like mine, or your mechanical skills may be rusty, or...well, there are myriad reasons why you shouldn't attempt this repair or the information may not be valid. Caveat emptor!
Disclaimer #2: Let me say that I know my van is dirty, which is documented in the pictures. The past two places we lived had red clay soil, which stains on impact. There are also three teens in my family and occasionally our pet golden retriever rides with us, especially when we camp, so yes, we use our vehicle and it doesn't get cleaned nearly enough...surely I am not the only person in America with stained carpet and dirt on their floor (I did vacuum the van after these pictures were taken--out of guilt).
Disclaimer #3: Some of the photos are terrible. I used to be very critical of some of the out-of-focus pictures I saw on the web, but now I understand why they are so bad: Trying to get a close up shot, using only one hand, in a dark van, while holding the part being photographed with the other hand, is a feat!
So, here goes....
First, disconnect the battery. Doing this will allow you to use an ohmmeter without worry of finding a voltage by accident (which could be devastating to your meter). This will also prevent the airbag from exploding in your face, an event that would ruin your day.
Second, check the horn steering column to see if you have a good ground. This will help diagnose the problem to make certain that the effort you exert for this repair will be a good investment.
Connect your ohmmeter to a good ground. I used a battery clamp attached to the lighter plug and accessory plug (see photo). Any metal part of the car body will do for a ground, but finding a metal part on a plastic car can be difficult...
Next, check your steering column for ground. To do this make certain your meter is properly operating and connected to ground by shorting the meter leads and noting the zero on the meter. When the leads are not touching the resistance (ohms) should be infinite. With one probe connected to your "established" metal ground (the lighter plug, in my case) probe around on the care body to find another metal spot that is ground. Once you know that you have a good ground connection you can check your steering column for ground (i.e., conductivity).
To access the metal in the steering column I took a short piece of copper house wire and wrapped it around the probe tip to make a "probe extender." Take the extended probe and insert it into the narrow space between the steering wheel and the steering column. This is the only piece of metal I could find that was easily accessible (click on the photos to see a larger picture).
When you touch the extended probe to the metal at the base of this narrow gap, it should read zero ohms (i.e., it has a good ground). If you get a reading that shows resistance, then there is a good chance the problem lies in those pesky bearings. (note: the photo shows the steering column with the covers removed. You don't have to remove the covers to access this area).
Okay, now that you've determined your steering wheel is indeed not grounded, let's get those bearings greased and see if that solves your problem.
Remove the covers from the steering column. To do this you will need to first remove the kick plate, door jamb panel, and "panel sub assembly" (I don't know the correct terms for these items, so I'll describe each piece the best I can). The kick plate is the plastic cover that is adjacent to the carpet on the floor and is covered when the door is closed. Gently pull on it with some force and it will give way. I slowly pulled mine by getting my fingers underneath it on the seat-side and slowly tugging at it, trying to be careful to not break any plastic "trim retainers" hiding underneath.
Next remove the door jamb panel (this is the panel that covers the lower area of the door jamb next to the emergency brake. You'll need to removed this to access the left side bolt of the panel sub assembly). Just gently pull on this and it should come loose, being careful to not break any plastic "trim retainers" hiding underneath.
Now you can remove the lower part of the dash called the "panel sub assembly" (where coin holder is located). To do this, remove the 10mm bolts on each side of the panel sub assembly and then gently pull the piece down. You'll notice the tire air reset button is located here. I used a small flat-head screw driver to disconnect the wires from the button so I could lay this panel on the floor
You're almost there (this all sounds much worse than it is. It was really a pretty simple job, except for the 95 degree temps and 50% humidity). Next take a Phillips head screw driver and remove the three screws holding the steering column cover in place. One screw is directly under the steering column (easy to get to). The other two are located on the left and right side of the steering column, directly under the steering wheel (odd places to have a screw). To access these two you will need to rotate the steering wheel 90 degrees to the right to access the left screw and then, beginning at center again, rotate the steering wheel 90 degrees to the left to access the right screw. At this point the bottom half of the steering column cover should drop to the floor and the top should be able to be lifted up (but probably not come completely off).
Now you can see the guts of this beast. The bearings you're looking for are here (click on photo for more detail):
To clean and lube these babies use a spray lubricant with a straw (tube) stuck in the nozzle and a rag held underneath the steering column to catch the excess lubricant.
I began with some electrical contact cleaner spray. That seemed to do no good, because after spraying it into the bearings I still measured "infinite" when I placed the extended probe at the steering wheel. From there I changed my course of attack and used a multi-purpose lube (see comments below for other suggested lubricants, such as a copper lube), and this worked. I sprayed, rotated the steering wheel 90 degrees, sprayed more, rotated back the other way 180 degrees, sprayed more, etc., all the time holding a rag underneath the steering column to catch the lubricant that was trying to drip on to my "sub panel assembly" sitting on the floor (note: one reader said that on some vehicles (not a Toyota), rotating the steering while the engine was not running damaged the power steering seals. I didn't have that mishap occur, but caveat emptor!)
Another check with the ohmmeter showed that the steering wheel was grounded...yippee! I reassembled the dash, hooked up the battery--which set off the car alarm, so keep your remote for your alarm handy. I then pushed on the steering wheel horn and wha-la, it worked!
After looking at the filthy floor of the van for the past hour I decided to break out the shop vac and vacuum the front half of the van, leaving the remainder for my children to clean.
Good luck with your repairs. If anyone has other tips please share.