Great question! From what I’ve experienced, the Face ID hardware is similar to touch ID hardware in that it is tied to the phone’s logic board. However, FaceID does seem a little more forgiving. The phone I’m currently using is an iPhone X that was severely damaged. I bought it off a customer and installed a new screen but Face ID did not work. A couple months later, I was using an app that made use of face ID hardware for facial recognition and mapping. I thought it wouldn’t work since FaceID wasn’t working on my phone. To my surprise, it worked just fine. I then tried setting up FaceID and it was able to activate and capture my face.

If you’re looking to refurbish a phone, assume FaceId won’t work without the original hardware. However, your milage may vary.