1. Try changing the data cable (use the original / default device)
2. Replace the USB slot
3. Please check iTunes checks whether or not the latest update. on the taskbar iTunes click Help> Check For Updates
4. Do a hardware reset on the iPhone
If all the 4 above option is not working then it is hardware problem which could means two things one is faulty dock flexible or faulty chipset IC to usb controller on the iPhone logicboard.
How to do a hardware reset on iPhone:
1. Power on the iPhone.
2. Hold the Home and Power button for about 7 seconds, or until the screen turns black.
3. Waits for your iPhone to reboots.
How to do a Force Restore on iPhone:
1. Turn off your iPhone by pressing the Power button for about 5 seconds or until the Slide to active Power slider appears.
2. Power Off slider. If the iPhone is unresponsive, follow the instructions of Hard Reset to Step 3. Open iTunes on your computer (Mac or PC).
3. Press and hold the Home button while you connect the iPhone to the computer iTunes will issue a notice iPhone has been detected in Recovery Mode and that you have to Restore Click Ok.
4. Click Restore Confirm that you want to Restore and Update.
Restore has begun. Leave your iPhone connected to reboot your iPhone and sync with iTunes. If the above steps are not successful, there may be a hardware problem, wait until there is error message iTunes and refer to the error message iTunes we can determine the cost of servicing your iPhone. please contact us at +6281289310080 to fix it as we can help to fix the problems .Jasa Service iPhone Spare Parts Mac Komputer Di Jakarta Mangga Dua Mall , Harco Mangga Dua , Mall Ambassador Apple-lab tokos.