I have the same issue. Before this problem appear, the iPhone 6 sometimes does not connect to iTunes, nor charge. Before die I set to WiFi sync and now I can sync (slow, but I can).
Son now there is no way to charge connected with a genuine cable to any PC/MAC, also can't connect to iTunes via USB. I find a fix for charging it connecting to a PC, but not for USB data connection.
Using a microUSB to lighting adapter and a USB-MicroUSB cable for power only, you can charge with a PC.
Is not easy to find a USB-MicroUSB cable with only power wires and no data wires. Normally this kind of cable are together with a power bank battery.
The iPhone problem, probably have not any solution. At the Genius bar, after many tests told me that is the Logic Board. If iPhone is out of warranty, you need to spend a lot to replace the phone.
Who have this defect, and out of warranty, can't do nothing. The phone is 99% working except the USB sync function. If you have enabled the WiFi sync (Before USB die) you can use the phone without problem, also you need to use iCloud for save your data. Probably the USB chip inside the phone is damaged, and to make full working the phone, need to be replaced, but, replace it is really complicated and not cheap, also the risk to kill the phone is really high.