How To Fix an iPhone 14 That Randomly Restarts

How To Fix an iPhone 14 That Randomly Restarts
Device	iPhone 14, iPhone 14 Plus
Affects part(s)	Main Logic Board
Needs equipment	Screwdrivers, known good parts, spudger
Difficulty	◉◌◌◌ Easy
Type	Part replacement

Problem description

There are many reasons that could cause an iPhone 14 and iPhone 14 Plus to randomly restart every few minutes. For the iPhone 14 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 14 series are:

Back Glass/Wireless Charging Flex- This is the flex that is attached to the Back Glass. It can damaged during a drop or screen replacement
Proximity Flex -This is the flex that is attached to the screen. It can easily be liquid damaged or torn during a screen replacement.
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.

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.
iPhone 14 With Back Glass unplugged. This causes 3 min restart. Panic Log Code 0x400000
After a screen repair, the iPhone will bootloop every 3 minutes
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:

0x400000 - it's the Wireless Charging Flex (Back Glass)
- iPhone 14 With Back Glass unplugged. This causes 3 min restart. Panic Log Code 0x400000
  Make sure it's plugged in & the flex is not torn
- Check that there's no liquid damaged, or that it's defective
- Test with OEM or Premium. Aftermarket Flexes have a high defect rate
- Diode mode the FPC connectors for any faults
- Could be a sandwich issue

iPhone 14 Panic Log Example. Charging Port Flex unplugged. This causes 3 min restart. Panic Log Code 0x100000
0x100000 - it's the Charging Port Flex
0x500000 - Check the taptic engine as well as the charging port flex
- 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 faults
- Could be a sandwich issue

iPhone 14 Panic Log Example. Prox Flex unplugged. This causes 3 min restart. Panic Log Code 0x200000
0x200000 - it's the Proximity Flex Cable
- 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
- iPhone 14 With Proximity Flex unplugged. This causes 3 min restart. Panic Log Code 0x200000
  Diode mode the FPC connectors for any faults

0x500000 - it's a communication problem with the battery
- the battery has a communication issue while charging
- restarts every 3min30sec
- test with another battery
- check diode values on battery connector on the motherboard
0x600000 - it's wireless Charging flex + proximity Flex Cable
- check with original known good flex
- both must be connected to the motherboard

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 plugged in. Otherwise, it WILL restart. You cannot troubleshoot this step by unplugging the bad flex.