I also had a problem with my transfer indicator switch. My dealership wanted $90 for the part and about 1 week to get it. I had success with just cleaning the switch instead of having to buy a new. Just finished a write-up on it in case anyone's interested:
Transfer Indicator Switch Problem with 4WD Toyota/Lexus Center Differential Lock
I know I don't have a Tundra, but the transfer indicator switch seems to be a problem common with a lot of Toyota/Lexus 4WD vehicles like the Tundra.
Thanks,
Clifford A.
2000 LX470