What makes you think the fault is software related?
Did you notice the issue after an update / jailbreak attempt?
Firstly, try resetting / restoring to see if that works.
If not, then I would say disassemble and check your connections, especially cable 2 at the top end of the phone.
Did you definitely buy the right version of touch and fully secured it?
Sounds stupid but you wouldnt believe how many I repair with the wrong touchscreens on or the cable only half way home.
Hope I helped.