Need to program a 2nd key for my 2004 Toyota Sequia. I have one key that works now

remote key by using OBDSTAR X100 Pro auto key programmer

you need service and repair manual to fix the problem by your own and to get the manual go to the given link http://toolsnyou.com/

key codes are dealer issued --if you have a good working key their are some locksmiths and a few stores [some larger named hardware,home stores ] can cut certain electronic keys the following links show how to do programming on certain 04 toyota s but its even specified in links that it doesnt work all the time
2004 Toyota Sienna LE Immobilizer Key Programming How To Toyota Ignition Key Programming

Mate here's a link for a Utube video showing how to program a Toyota Tundra replacement remote programming 2004-2006... It's the very 1st video at the top
CHEERS.....
https://www.youtube.com/results?search_query=Toyota+Tundra+Replacement+Remote+Programming+2004+2006

Hi found this link when researching your post , it would appear the 2004 sienna has to go to a dealer to be programmed , follow this link and see what you think about it
Toyota Transponder key programing

by what your saying the key that you are using has a chip in side of it some times if the key goes near a magnet it will kill the program in the key. if you have a spare key try that key. if you don't what you might have to do is bring your car and key to the dealer to have them programed. but that red key on the dash board is telling you that sercurity has been turned on so that no one can steal it with out that key that you have. try that good luck

try crutchfield.com

sit in car all doors closed put key in ignition and turn from OFF to ACC 3 times as fast as you can leaving it in ACC on the last cycle then press your remote button. your blinkers should flash to tell you this has worked.... may take you a couple of tries to get it!!

you need to take it to the dealer so they can program the key to the car which requires there software. hope this helps

........You need to take the the unprogrammed key, and the vehicle, to a Toyota dealership. They have an electronic tool that teaches the key the program specific to your vehicle. There is no other way to do it. I provide the reprogramming procedure for free, as a courtesy to our customers.