Q&A

To replace the ignition lock assembly the air bag needs to be disarmed, the steering wheel removed, the steering column trim panels removed and when the key is placed in the ignition switch a small detent at the top of the switch can be depressed allowing the ignition switch locking mechanism to be withdrawn from the steering column. A mechanic should do this but a lock smith may be able to do the job as well.

just had the same problem diagnosed by a locksmith. Ther eis a small casting about 1/8 " thick by 1/4 " by 3/8 "that is in the tumbler. This piece was worn out . it has something to do with the anti theft locking device for the steering wheel.

I've had the same problem with my 2001 Toyota Avalon. It's even mentioned as a possible problem in the owners manual. The manual says to wiggle the steering wheel (left to right) while turning the ignition switch. This has worked for me. You have to wiggle the steering wheel at the SAME TIME as you turn the key in the ignition switch or it doesn't work.
Also, when I went to the dealer about the problem they said that it almost never requires a new ignition switch. The problem is almost always caused by the key wearing down with use over several years and not fitting in the ignition switch properly. They made me a new key from the original serial code specifications for my key and the problem happens much less often.