How do I get my radio unlock code?

There might be a specific reset procedure that must be followed for safety reasons when the airbag circuitry is disconnected. You will need the maintenance manual to determine the proper procedure. Also make sure all of the connections are correct.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/dave_fb2c45146b845cea

first off you should have a dealer that installers the alarms, that way they would of ordered the correct alarm system, that way all would work

Hate to state the obvious, but have you checked fuses and fuseable links? Was neg. bat. term. disconnected when you were working on this? Reconnected?

Once the car is up and the plastic shield underneath is removed, there really isn't too much to it, disconnect the battery but be sure you have your radio code{usually in owners manual} then just a couple of bolts and 1 terminal and 1 plug and its out, on the scion he may have to remove a side bracket {easy} all in all about 1 hours work in and out. Basic mechanics can do this. good luck.

possible soldier joints in the frob, or battery is bad, if new battery, then where battery connects in frob,is not making good contact

only possible if the steering wheel bag sensor is at fault
If it is a passenger bag , would not be affected
run the fault codes to determine the exact fault area /sensor

I had that issue with my scion xb. When I installed my audio system somehow the vibrations loosened the button wires clip . I removed the door panel and clicked it back in, also it could be a dead solenoid or disconnected door wire that goes from the 'noid to the door lock pin.

No i have pulled out the stereo myself and there is no port for it, that option is now offered on the 2008 which sucks because they where giving ipods away at the dealership when i got my 05 Scion xb makes no sense huh.

For $20 US you can access the Chilton service manual here:
http://www.chiltondiy.com/

I personally prefer hard-copy and have either Haynes or Chilton for each of our vehicles. One or the other (probably Chilton - Haynes doesn't yet list the Scion line) will be found in just about any auto parts store and cost between ~$17-$30 US. The two lines are owned both by Chilton and I wouldn't be without one or the other. They are both based on a complete rebuild and have info on anything you can do at home and more.