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How To Fix an iPhone 11 That Randomly Restarts
Device	iPhone 11
Affects part(s)	Main Logic Board
Needs equipment	Screwdrivers, known good parts, spudger
Difficulty	◉◌◌◌ Easy
Type	Part replacement

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Problem description

There are many reasons that could cause an iPhone 11 randomly restart every few minutes. For the iPhone 11, 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 11 series are:

• Bad or Defective Battery - If the phone is not showing a percentage at the top of the screen, it means the battery data isn't being read by the device, causing the device to restart. So if you see your iPhone 11 says it's charging at 0%, that could be why it's restarting.

• Charging Port Flex - This is the flex towards the bottom of the phone which is slightly exposed behind the back glass. It is easily damaged with a drop & broken back glass, or by a technician during a back glass repair.
• Damaged or Defective Power Button - There is a secondary mic (mic2) that is on the power button flex. It is easily damaged, especially after back glass repair, causing the mic to be disconnected & the phone will restart when it's not detected.
• Motherboard Sandwich Separation - If an iPhone 11 has a hard drop, it can cause the 2 layer sandwich to separate, which will disconnect the mic2 line from the power button flex, as that connect is on the bottom board. So it may need a sandwich reball to repair it.

Symptoms

• After a back glass repair, the iPhone will restart on its own every few minutes
• After a battery replacement, 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 "Missing Sensors:.."

An example of panic log files you'll find in the iPhone when it has been randomly restarting.

If you see:

• TG0B or TG0V - It's battery related:
  • The battery is defective or has failed
  • The battery connector itself is damaged, warped or broken
  • The battery connector data lines are missing.
    • Check the battery data pins (I2C2_SMC_SCL_CONN and I2C2_SMC_SDA_CONN) for a diode mode reading. If it's OL, check the resistors R3202 and R3201 for damage. Otherwise, the disconnection could be under the CPU & requires a CPU reball. If you get a short, then check the caps around the connector. Otherwise, the short is within the CPU likely not fixable.

• Prs0 or Mic1 - It's the charging port flex.
  • 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
  • Check for damaged or missing resistors around the charging port connector
  • Check R6822 (I2C1_AOP_SCL) and R6823 (I2C1_AOP_SDA) resistors

• Mic2 - It's related to the mic on the power button flex
  • Test with a known good power button flex
  • Check for pry damage on all the small components near the connector
  • Diode mode the power button connector & see if you get an OL. If so, you may have to split the sandwich and check for mic2 lines and ripped pads. You may need to reball the sandwich to fix it.

An example panic log, showing "Missing sensors: Prs0", which means it has a bad charging port flex.

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 parts on your bench, for testing only. There are reports of even NEW parts 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.