Admittedly, it is quite irritating that you get a notification of "iPhone could not be restored. An unknown error occurred (4005)" while attempting to restore iPhone or update iOS. As an iPhone user, it is greatly possible to experience the dread iPhone error 4005. Basically, this particular error means that updating or restoring process will not be successful and leaves you with an iPhone that cannot be updated. Maybe you think it is a serious matter that needs to be settled as soon as possible. Actually, you don't have to worry too much. This tutorial will set forth 6 workable methods to work for you regardless of the causes.