Recently we started having problems turning my 2000 Sienna's key in the switch past the OFF position. I have to wiggle the wheel for some time and play with the key, until it "catches" the right position to turn to ACC position. Looking for a solution, I found a video on Youtube describing how to replace the switch tumbler.
After goofing around for some hour or so, trying to open the dash panels, I was finally able to extract the tumbler out of the switch assembly. I also found a non-OEM part on eBay for $35. Then, I called the local dealer to see if they have it in stock, and to my surprise, after getting the VIN, he quoted ~$240 for an original part. When I told him I found it online for $35, he said that it is b/c my key has the immobilizer chip in it, and he guarantees that the replacement part will not work.
Further investigating, I found out that the chip (transponder) is embedded in the key, but the antenna is in the ring around the cylinder, and not in the part I took out. So, I now know that there are unchipped keys, which are slim, and chipped ones which are "fat".
Is there a difference between the tumbler parts of a chipped and unchipped switches? Can it be safely interchanged inside the switch assembly?
One reference demonstrated how to ignite the car using an unchipped key, while holding an original chipped key just next to the antenna ring (the ring around the keyhole). Does the engine continue working even long after the chipped key removed away from the switch, or is there some repeated ID conformation every couple of minutes?
Is the orientation of the transponder (the chip) with respect to the antenna critical for successful communications?
Update 1: It happens that when inserted in place, the rear side of the tumbler rotates a small flat piece that is connected to the actual electrical switch. When removed the housing looks like a big empty cylinder with this metal piece sticking up from its far end (think about an 12V accessory (cigarette lighter) socket with a metal blade popping up inside, where the positive 12V contact is placed normally).
In order to remove the tumbler, one has to rotate the key to the ACC position. So, when removed, the flat piece is slightly rotated inside that hollow cylinder. Now, I was able to use pliers to grab and rotate that piece, as if it was the tumbler - and so turn the car on, while holding my transponder key near the removed antenna ring.
The car does turn on and remains on even while the key was removed from the antenna. It kept running until I used the pliers again to rotate the piece back to ACC mode. So, I guess this answers my questions #2 and #3.
I thought about leaving the switch like this and using the pliers method until the replacement tumbler is shipped, to avoid getting stuck with an dis-functioning key switch (which will later prevent me from extracting the tumbler again). Unfortunately, once in ACC, the pliers cannot rotate the metal piece back to OFF position, so the car remains half operational all the time. Eventually, I placed the part back in place and turned off all systems.