iPhone 8, X, XS, XR, 11, 12 and SE restarting every 3 minutes

On iPhone 8 to 12 and the SE models, a restart about every 3 minutes means iOS lost one of its sensors. The panic log says Missing sensor(s): followed by the sensor name - here is which part each name points to, and what real repairs showed.

What the panic log says

iOS checks its sensors every 3 minutes; when one does not answer, the phone restarts - again and again until the part is fixed.

Missing sensors and their parts

Some parts must be connected for the phone to stay on: on iPhone X, XS and XS Max the charging port flex; on the iPhone 11 series both the charging port flex and the power button flex (VCC Board Repairs).

What repairs showed

• Fixed: an iPhone 11 whose charging flex was damaged during a back-glass repair - a non-original replacement did not help, an original flex did ("Everything work as well!"). ^{iFixit case}
• Fixed: another iPhone 11 with mic2 - a new power button flex, "all goes well". ^{iFixit case}
• Not the named part: after liquid damage an iPhone 11 named prs0, but the real fault was a corroded volume flex shorting the same data lines. ^{iFixit case}
• Not fixed by a new flex: an 11 Pro Max kept mic2 after an original power flex; the line was traced to the board connector J7700 and the audio codec U4700. ^{iFixit case}
• Copies without the sensor: an iPhone XS kept prs0 after a charging port swap; the answers: many copies come without the sensor - fit a genuine port. ^{iFixit case}

Test order

1. What was repaired last? A screen, battery, charging port or back-glass job is the first suspect - the part fitted, or a cable disturbed during it.
2. Inspect the flex and its connector under magnification: torn traces, liquid marks, a bent pin.
3. Test with a known-good original part plugged in. Unplugging the cable does not test it - an unplugged sensor is missing too, so the phone still restarts.
4. Expect side effects: a replacement front sensor flex loses True Tone and auto-brightness; a battery or back glass that is not paired with Apple's System Configuration shows a parts message.
5. If a good part does not stop it, the fault is on the logic board (often after liquid damage) - micro-soldering.
6. Do not restore iOS for a hardware code. An SMC panic happens below iOS; restoring only costs time and, without a backup, your data.

Not the same problem

• No Missing sensor(s) in the log: a different panic - the analyzer reads those too.
• The phone will not update or restore (error 4013, 9, 75...): see the restore error lookup.

Sources

• iFixit: iPhone Kernel Panics
• iPad Rehab: Troubleshooting iPhone reboot problems
• VCC Board Repairs: panic log list
• iRepair Experts: iPhone random restarts and panic logs
• iFixit Answers: iPhone 11 thermalmonitord - fixed cases
• iFixit Answers: 11 Pro Max mic2 after a flex swap
• iFixit Answers: iPhone XS, prs0
• iFixit Answers: 12 mini, TG0B and TG0V