This is the step people miss. Repair Assistant is built into iOS and installs the calibration data that makes a new part work properly. To run it:
- Make sure the iPhone is on Wi-Fi, has more than 20% battery and is running the latest iOS.
- Open Settings, tap General, then About.
- Tap Parts & Service History.
- Tap Restart & Finish Repair and follow the on-screen steps.
On the iPhone 18 Pro models, the stakes are higher than on older iPhones: if you don’t finish the repair or restore the phone, the camera won’t work at all. On other models the phone keeps working, but the part may not perform as well. Face ID and Touch ID won’t unlock your phone, approve payments or sign you into apps until those parts are calibrated.
One exception: on the iPhone 18 Pro and Pro Max, replacing the back glass doesn’t need Repair Assistant.
If Repair Assistant fails, check the part is seated correctly, restart and try again, or try another part. A part taken from someone else’s phone might be protected by Activation Lock. If it stays locked, it won’t be covered by Apple’s warranty or AppleCare, and you can’t trade the phone in.