Chosen Solution
I was playing with iPhone 6 using Facebook and suddenly its touch screen stopped responding. I forced shutdown the phone and restarted the phone by pressing power and home button. When it came at Apple logo i saw some light grey vertical lines and touch screen stopped responding :( I tried resetting and updating the software. Where this problem possible can be? I tried replacing it with new LCD panel and it also didn’t work. See the image below. They are very light vertical grey lines
I would first inspect the physical digitizer connector (long one above lcd and front camera connector) and make sure all the pins look good. If they do it might be a touch ic problem. Standing lines w/ no touch or intermittent touch is classic for touch ic problems.
