I have an iPhone 6+ that was given to me by the original owner because she thought she had bricked it while attempting to set it up for a family member.
Using DFU mode I have un-bricked it, but one problem remains, I can't set up Touch ID. During initial setup, & every time I've gone to set Touch ID up in the Settings app, I see the setup screen for less than a second before it goes to a screen saying, "Failed Unable to to complete Touch ID setup. Please go back and try again." I've tried with a SIM installed & that makes no difference.