How to Troubleshoot an iPhone That Will Not Connect to a PCby Aaron Parson
The iPhone can function without connecting to your PC, thanks to services such as iCloud backup and the ability to download iTunes purchases directly on the phone. Nonetheless, syncing with iTunes on your PC is the fastest way to transfer playlists, app updates and files to the phone. When your computer won't recognize the phone, you may have a damaged piece of hardware or a software glitch on either the phone or the computer.
If a previously working iPhone suddenly stops connecting to your PC, one of the hardware components may have broken. The iPhone USB cable can break from rough treatment, causing intermittent dropouts or complete failure. If possible, try using a different USB cable. Though less likely, you may have also damaged the USB port on your computer or the port on the iPhone. Try using a different USB port on your PC.
Updating and Reinstalling ITunes
You must have a working copy of iTunes on your PC to connect your iPhone. If you haven't used iTunes before, download it from Apple's website (see Resources). Apple also recommends updating to the latest version of iTunes to resolve potential issues. If you already have the latest version of iTunes, try uninstalling it and reinstalling it from a new download. This may clear up glitches in the system that are preventing your phone from connecting. Apple also notes that some connectivity programs from other phone manufacturers can interfere with iTunes. Uninstall any such programs you have before reinstalling iTunes.
Checking the USB Driver
Reinstalling iTunes should set up the USB driver for your iPhone automatically, but you can check the driver's status manually if you continue to have problems. With your iPhone connected, press "Windows-X" and open the Device Manager. Open "Universal Serial Bus controllers" and look for "Apple Mobile Device USB Driver." If this entry's icon has a down arrow, right-click it and pick "Enable." If it displays an exclamation point or question mark, right-click it, pick "Uninstall" and press "OK." Open the "Action" menu and click "Scan for hardware changes" to reinstall the driver. If your system cannot find the driver automatically, you can manually locate it at C:\Program Files\Common Files\Apple\Mobile Device Support\Drivers\usbaapl64.inf.
If no other steps work, wiping your phone may solve the issue, but will erase your data -- though you can recover data later from an iCloud or iTunes backup. On your phone, open the Settings app, tap "General," "Reset" and then "Erase all Content and Settings." After the phone formats, try connecting it again. If it still won't work after all these methods, your phone may have a damaged connector internally and require professional repair.
Wi-Fi Sync Workaround
If your iPhone won't connect via USB but you don't want to send it in for repairs, you can still sync with iTunes if you have previously set up Wi-Fi sync. If you ever checked "Sync with this iPhone over Wi-Fi" in iTunes, your iPhone will appear in iTunes any time both your phone and computer are connected to the same network. Wi-Fi sync can perform all the same operations as a regular USB sync.