I just purchased a 99 SLE and the theft lock is activated. I want to install an aftermarket radio. The previous owner has no idea what code was put into the radio. My question is how do you deactivate the lock so the radio can be installed at a later time and still work?

It needs to be taken to a dealer and hooked up to a tech2

Is that an expensive proposition?

I have no clue. Depends on the dealership.