Seven Things You Can Do to Troubleshoot iPhone Issues
If your iPhone is frozen or otherwise acting up, perform these troubleshooting techniques, the seven Rs, in sequence. You should recharge your iPhone, restart your iPhone, reset your iPhone, remove content from your iPhone, reset your iPhone's settings and content, restore your iPhone, and renew your iPhone in Recovery mode.
Recharge your iPhone
If your iPhone acts up in any way, shape, or form, the first thing you should try is to give its battery a full recharge.
Don’t plug the iPhone’s Lightning connector cable (iPhone 5) or dock connector–to–USB cable (earlier models) into a USB port on your keyboard, monitor, or an unpowered USB hub. You need to plug the cable into one of the USB ports on your computer itself or a powered hub (one that requires an AC power source) because the USB ports on your computer supply more power than the other ports.
Note that you can use the included USB power adapter to recharge your iPhone from an AC outlet rather than from a computer. So if your iPhone isn’t charging when you connect it to your computer, try charging it from a wall outlet instead.
Restart your iPhone
Just as restarting a computer often fixes problems, restarting your iPhone sometimes works wonders.
Here’s how to restart:
Press and hold the sleep/wake button.
Slide the red slider to turn off the iPhone, and then wait a few seconds.
Press and hold the sleep/wake button again until the Apple logo appears on the screen.
Reset your iPhone
To reset your iPhone, merely press and hold the sleep/wake button while pressing and holding the Home button on the front. When you see the Apple logo, you can release both buttons.
Resetting your iPhone is like forcing your computer to restart after a crash. Your data shouldn’t be affected by a reset. So don’t be shy about giving this technique a try. In many cases, your iPhone goes back to normal after you reset it this way.
At this point, it’s a good idea to back up your iPhone’s contents by right- or Control-clicking the phone's name in the list on the left side of the iTunes window (on your Mac or PC) and choosing Back Up. Or you can initiate a backup to iCloud from your iPhone by tapping Settings→iCloud→Storage & Backup→Back Up Now.
Remove your content
Nothing you’ve done so far should have taken more than a minute or so (or 20 if you tried the 20-minute recharge). That’s about to change because the next thing you should try is removing some or all of your data, to see whether it’s the cause of your troubles.
To do so, you need to sync your iPhone and reconfigure it so that some or all of your files are removed from the phone. The problem could be contacts, calendar data, songs, photos, videos, or podcasts. If you suspect a particular data type — for example, you suspect your photos because whenever you tap the Photos icon on the Home screen, your iPhone freezes — try removing that type of data first.
Reset your settings and content
Resetting involves two steps: The first one, resetting your iPhone settings, resets every iPhone setting to its default — the way it was when you took it out of the box. Resetting the iPhone’s settings doesn’t erase any of your data or media.
The only downside is that you may have to go back and change some settings afterward, so you can try this step without (much) trepidation. Tap the Settings icon on your Home screen, and then tap General→Reset→Reset All Settings.
Be careful not to tap Erase All Content and Settings, at least not yet. Erasing all content takes more time to recover from (because your next sync takes a long time), so try Reset All Settings first.
At this point, you could try resetting some of the other options available on the Reset screen, such as Reset Network Settings. If you’re desperate, it won’t hurt to try Reset Keyboard Dictionary, Reset Home Screen Layout, and Reset Location Warnings; they’re not likely to help but might be worth a try before you resort to erasing all content and settings.
Now, if resetting all settings didn’t cure your iPhone, you have to try Erase All Content and Settings. You find that option in the same place as Reset All Settings (tap Settings→General→Reset).
Restore your iPhone
Restoring your iPhone is a fairly drastic step, but it often succeeds after recharging, restarting, resetting, removing content, and resetting settings and content have failed.
To restore your phone, connect it to your computer as though you were about to sync. But when the iPhone appears in the iTunes source list, click the Restore button on the Summary tab. This action erases all your data and media and resets all your settings.
If your computer isn’t available, you can trigger this step from your iPhone by tapping Settings→General→Reset→Erase All Content and Settings.
Renew your iPhone with Recovery mode
If you’ve gone through all the previous suggestions or you couldn’t attempt some or all of them because your iPhone is so messed up, you can try one last thing: Recovery mode. Here’s how it works:
Disconnect the USB cable from your iPhone, but leave the other end of the cable connected to the USB port on your computer.
Turn off the iPhone by pressing and holding the sleep/wake button for a few seconds until the red slider appears on-screen, and then slide the slider.
Wait for the iPhone to turn off.
Press and hold the Home button while you reconnect the USB cable to your iPhone.
When you reconnect the USB cable, your iPhone should power on.
Continue holding the Home button until you see the Connect to iTunes screen, and then release the Home button.
If you don’t see the Connect to iTunes screen on your iPhone, try again from Step 1.
If iTunes didn’t open automatically already, launch it now.
You should see a Recovery Mode alert on your computer screen telling you that your iPhone is in recovery mode and that you must restore it before it can be used with iTunes.
Use iTunes to restore the device.