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Sony Xperia U Troubleshooting
Phone will not connect to or recognize networks.
From the home screen, press Menu - Backup and reset - Factory data reset - Reset phone. It may ask for a password. Then select erase everything.
The battery is broken or damaged.
Replace it with a manufacturer original or a respected third-party unit. In our experience though, third-party batteries are often cheaper but more trouble than they are worth, and can even be damaging to your device, so use one at your own risk.
Phone freezes and then shuts down.
Turn off applications that aren't being used. Use extended standby mode when screen is inactive to minimize battery consumption. Lower screen brightness level.
All you have to do is hold the Volume Down button and then the Power key and hold these two buttons down simultaneously for about 15-20 seconds. After holding them down for about 20 seconds if the phone didn't power cycle then release the keys and try and turn the phone on like you normally would by briefly pressing the power button.
Doesn't connect to a network, doesn't receive calls or messages.
Make sure you have set your device to use the correct network type. If your subscription plan does not support the LTE (4G) standard, you must select a network type other than LTE (4G). If necessary, contact your operator for more information about your subscription and the network types supported.
Replacing the Camera.
Replacing Headphone Jack.
Replacing the Loudspeaker Module.
Replacing the Motherboard.