So please clarify. You say it does it when not moving but on full lock !!? So nothing is moving and it squeeks?
OR - does it squeek when you turn the steering wheel and the car is not moving (so not on full lock but going towards full lock?)
If it is related to the steering being turned then it could be the steering column bearing, the rack or gaiters or the clock spring behind the steering wheel that relays all the wiring to the steering wheel controls.
Need to narrow down when it squeeks!!