There are many reasons that could cause an iPhone 15 Pro and iPhone 15 Pro Max to randomly restart every few minutes.
For the iPhone 15 Pro series, there are some sensors within the parts of the phone that are required to be plugged in & detected. Otherwise, the phone restarts on its own.
The most common for iPhone 15 Pro series are:
Charging Port Flex - This is the flex towards the bottom of the phone. It is easily damaged with a drop & the back glass is breaks. Or when someone has repaired the back glass.
Back Glass/Wireless Charging Flex - This is the flex that wraps around the logic board & controls the power button.iPhone 15 Pro Max - Wireless flex diagram. If it's unplugged, it will restart giving panic log error 0x400000
Bad Battery - If the battery is defective or goes bad, it can cause restarting problems.
Proximity Flex - iPhone 15 Pro Only - If the prox flex is unplugged, damaged, or defective, it can cause 3 min restart problems. This does not apply for the iPhone 15 Pro Max.
Symptoms
After a back glass repair, the iPhone will restart on its own every few minutes
After a hard drop, the iPhone will restart every 3 minutes.
After a screen repair, the iPhone will bootloop every 3 minutes
After replacing the charging port flex, the device will auto restart on its own randomly.
The iPhone will reboot randomly when using it.
The iPhone will seem to freeze and restart every 2-5 minutes.
Solution
Diagnostic Steps
Before you start blindly replacing parts, it's important to try to confirm what is causing the restarting issue by reviewing the Panic Log file. This is a file that is generated by the Operating System, to document the fault causing the restart.
To find the panic log on the device, go to Settings-> Privacy-> Analytics & Improvements-> Analytics Data-> Scroll down to the files starting with "panic-full..." & click on the most recent dated file.
Then you'll want to scan through the text for keywords that may point you to the cause.
For this model, look for where it says "SMC PANIC - ASSERTION FAILED" ... "Sensor Array" .. "0x...."
If you see:
0x200000 - It's the Proximity Flex
Only affects the 15 Pro and not the 15 Pro Max
Make sure this flex is plugged in
Check that no flex is torn, liquid damaged, defective
Test with OEM or Premium. Aftermarket Flexes have a high defect rate
Diode mode the FPC connectors for any fault
0x300000 - It's the Charging Port FlexiPhone 15 Pro Max Panic log example. It will restart if the charging port flex is unplugged, causing 0x300000 panic log error
iPhone 15 Pro Max will restart if the charging port flex is unplugged, causing 0x300000 panic log errorMake sure this flex is plugged in
Check that no flex is torn, liquid damaged, defective
Test with OEM or Premium. Aftermarket Flexes have a high defect rate
Diode mode the FPC connectors for any fault
0x400000 - It's the Wireless Charging Flex on the Back Glass
Make sure this flex is plugged in
Check that no flex is torn, liquid damaged, defective
Test with OEM or Premium. Aftermarket Flexes have a high defect rate
Diode mode the FPC connectors for any faultPanic Log Example of 0x400000, which is due to the wireless charging flex being unplugged
0x600000 - It's 2 problems, the Proximity Flex and Wireless Charging Flex
Make sure both flex cables are plugged in
Check that no flex is torn, liquid damaged, defective
Test with OEM or Premium. Aftermarket Flexes have a high defect rate
Diode mode the FPC connectors for any fault
0x700000 - It's 2 problems: Charging Port Flex and Wireless Charging Flex
Make sure both flex cables are plugged in
Check that no flex is torn, liquid damaged, defective
Test with OEM or Premium. Aftermarket Flexes have a high defect rate
Diode mode the FPC connectors for any fault
0xa1 - It's a battery data issue.
Sometimes you'll see the battery percentage fluctuate or you'll randomly get a "non-genuine" message.
Check the battery connector pins. Sometimes they can bend out & battery won't make good contact.
Diode mode the battery connector pins & compare them to known good board
Test with a known good battery
Replace the battery connector
iPhone 15 Pro Max - Device will restart every 3 minutes if the battery is bad, giving error 0xa1
Alternatively, you can use a tool like the iDevice Panic Log Analyzer, which will download the panic logs from the device & display them on the PC & give you suggestions to possible solutions. It makes it easier to browse the panic log file.
Also check out www.PanicFull.com which allows you to upload the panic log file & have it analyzed for free.
Both of these tools just give suggestions, which aren't always correct, as there is no official solution list from Apple. So many solutions are just suggestions based on hearsay, rumors or just guesses.
For situations where you don't see the above examples, you'll have to read through the top portion of the panic log & try to decipher what could be the root cause. Look for keywords you may recognize.
Repair Steps
When trying to solve for these issues, make sure to replace the appropriate flex with an OEM or Premium flex.
It is also a good idea to keep a known good power button flex & charging port flex in your bench, for testing only. There are reports of even NEW flexes being bad. So you have to keep known good flexes on hand at all times, so you don't waste your time troubleshooting with possibly bad flexes.
In scenarios where you have the appropriate flexes plugged in, but it still restarts, then you either have:
Bad or damaged flex
Low quality aftermarket flex
Other flex cables that are Liquid Damaged
Please note: You MUST have the required flex cables, (Charging port flex, Wireless Charging Flex, etc) plugged in. Otherwise, it WILL restart. You cannot troubleshoot this step by unplugging the bad flex.
