In this iOS 26 tutorial, I’m showing you how to put your iPhone into Apple Diagnostics mode so you can run a proper system check when something feels off—random reboots, battery weirdness, touch issues, or just a general “this doesn’t feel right.” The goal here is simple: get a clear report that can help you confirm whether you’re dealing with a hardware problem, a software issue, or nothing at all. I walk you through the exact button combo and the timing: charge your iPhone above 50%, make sure you’ve got stable Wi‑Fi, grab a Lightning or USB‑C cable, then power the phone off and wait about 30 seconds. After that, hold Volume Up + Volume Down, plug the iPhone into power while holding, and release when the Apple logo shows up. When the Diagnostics message appears, tap Start Session, connect to Wi‑Fi, accept the privacy terms, and let the checks run (it can take a few minutes). At the end you’ll either see detected issues on-screen or a message saying no issues were found—super useful before you contact Apple Support or head to a store.