Take a deep breath and see if your iPhone will turn on and operate normally. In most cases, the iPhone is still functional but now a cosmetic disaster. Unfortunately, the iPhone 8 Plus front glass and LCD are fused together and must be replaced as one piece.
You can purchase a new display assembly here.
The guide to replace the iPhone 8 Plus front panel assembly can be found here.
Even after furious button mashing and screen smashing, your iPhone 8 Plus doesn't respond.
Sometimes all it takes is a restart for the iPhone to become responsive again. To restart your iPhone when it is unresponsive, press and hold the volume down and power buttons until the Apple logo appears [~10 seconds].
It is possible for an iPhone to become unresponsive if the battery drops to an extremely low level. Plug the iPhone into your computer or wall charger and allow it to charge for at least 20 minutes before using it again.
Plugging in your iPhone 8 Plus does not bring it life.
Check the USB cable for damage and dirt, especially at the ends. Then try using the wall charger, as this will provide greater power input than the computer/USB.
Try using different chords, chargers and different wall outlets to see if there is a problem with your charger, cord, or wall outlet.
Inspect the Lightning connector at the bottom of the iPhone for dirt, lint, and damaged pins. Clean out the connector very carefully with a tooth pick or soft toothbrush. If the lightning connector is broken, you will have to replace it.
You cannot get your beloved iPhone 8 Plus to turn on.
Plug your iPhone into your computer or wall adapter to charge. If the phone does not charge when connected, the phone likely has a dead battery or a bad charging port. Replace the battery [using this guide here] with a partially charged one and see if the phone will turn on. If not, there may be a power button or logic board issue. If the phone does turn on, plug it in and see if the charging indication comes on. If the phone says it is charging, then the lightning connector works, and the problem is either the old battery or the logic board.
If the power button doesn't seem to work, plug the phone into the wall or a computer and let it charge. If the phone turns on and has power, then there might be a problem with either the power button or the power button cable.
It is possible that it appears nothing is happening because the display is bad. If the iPhone sounds like it is working properly but nothing is visible, it is possible the display is bad and must be replaced. Unfortunately, the LCD and glass panel are fused together, and must be replaced as one unit. An easy way to test this is to turn the phone on and listen for a sound. Also, you can move the mute toggle switch back and forth to see if it vibrates. If it vibrates or you hear a sound but nothing displays on the screen, then the screen is most likely the problem. Try replacing it and see if the display is still black.
You can purchase a new display assembly here.
The guide to replace the iPhone 8 Plus front panel assembly can be found here.
If nothing else works, your logic board is probably faulty and needs to be replaced. Now it is time to either replace it or diagnose if and what components are bad on the board and replace them, using microsoldering techniques. That is a whole 'nother beast!
If you have interest in chip level repair, you can start your investigation here!
You can get the materials to practice microsoldering here.
An error message appears as if you have connected an unsupported accessory to your iPhone.
Check the Lightning connector at the bottom of the iPhone for dirt, lint, and damaged pins. Clean out the connector very carefully with a tooth pick or soft toothbrush. Use high concentration isopropyl alcohol [at least 90%] and a cotton swab to clean any debris that does not come off with a tooth pick or soft toothbrush. If the connector is broken, you will have to replace it.
After an iPhone has been submerged in a liquid, there may be some corrosion or debris on the logic board connections that cause this error message. Remove the logic board and clean all of the contacts with a soft cotton swab and high concentration isopropyl alcohol [at least 90%].
You have trouble connecting to a wireless network.
If your iPhone has been disassembled before, it's possible that finger oils were left on the grounding locations for the Wi-Fi or Bluetooth antennas. These oils will cause grounding issues for the antennas, which could lead to a weak signal or no connectivity at all. Be sure to clean all grounding points with an electronics cleaning solution before reassembling your iPhone to prevent grounding issues.
Your iPhone 8 Plus turns on and appears to work, but when you plug in headphones or speakers, the audio doesn't play properly.
It's unlikely your headphones or speakers are bad, but it's worthwhile to eliminate these as the source of your problem at the beginning. Try your iPhone with different sets of headphones and speakers just to make sure that the problem is with the iPhone and not an external device.
The most likely cause of audio output problems on an iPhone 8 Plus is a bad lightning connector. If you have determined that the problem does not lie in your external speakers, you should replace the lightning connector.
Following a home button replacement, Touch ID features stop working.
As a security feature, your home button's embedded Touch ID fingerprint sensor is uniquely paired to your iPhone's logic board at the factory. If the original home button assembly is replaced, damaged, or disconnected, Touch ID features will cease to function.
Your iPhone is behaving erratically or displays the text "Use iTunes to restore" on startup.
It isn't often that Apple gives specific directions about how to fix your problem! Restoring the iPhone 8 Plus will erase everything on it, so make sure everything on the iPhone is stored elsewhere prior to restoring. To restore, connect your iPhone 8 Plus to a computer with iTunes installed. Click "Restore" on the iPhone 8 Plus summary page [click on your iPhone icon on the left menu to find this page]. Follow the directions to restore. If your iPhone 8 Plus displays the text "Please wait. Very Low Battery," leave it plugged in. This charges the iPhone enough to be able to restore. If the iPhone 8 Plus hangs on this screen for long periods of time, you may need a new battery.
If your iPhone 8 Plus is frozen with an Apple logo, or exhibiting some other software problem that prevents iTunes from recognizing it, you can force it into recovery/restore mode and then use iTunes to restore the software.
To force restart [hard reset] the iPhone 8 Plus, press and release the Volume Up button, press and release the Volume Down button, and press and hold the power button until you see the apple logo, then release.
After an accidental spill or a drop in the sink, your iPhone no longer works correctly.
As soon as possible, perform the following:
- Immediately remove the iPhone from the liquid [if safe to do so]. Minimize the length of time your device is in contact with liquid to prevent corrosive damage.
- Turn the iPhone off. [If it was off already, do not turn it on.]
- Skip the rice. Contrary to what you may have heard, rice is not an effective or lasting fix for water damaged electronics.
- Open the iPhone and disconnect the battery. [See your iPhone’s battery replacement guide for the correct procedure. You don't need to completely remove the battery; simply disconnect the battery connector from the logic board.]
- Liquid damage may complicate disassembly. Beware that some cables and connectors may be "adhered" to other components in unexpected ways.
At this point, inspect the interior of your iPhone and try to determine the extent of the liquid damage.