Shattered screen. Don't know if it's 1st or 2nd generation.
Just replaced the front display and rear glass on my Iphone4. I had one problem, but I think it was due to a manufacturing defect or an error during the assembly process at the factory. The headphone jack/volume control ribbon cable was covering most of the slot where the thin metal cover retaining clip resides. I didn't notice it during the disassembly process, but when I started to reassemble the thin metal cover, I noticed the ribbon was covering most of the slot and had an indention on it where the retaining clip had deformed it a little. The ribbon was covering all but an 1/8 inch of the slot where the retaining clip should fit. I had to file all but 1/8 inch of the clip off for it to clear the ribbon.
I finished the reassembly process and ops checked the iPhone4. IT ALL WORKED AS ADVERTISED! WiFi, Bluetooth, email, texts, phone; the works.
Thanks to Ifixit, I was able to accomplish a task I never thought I could successfully undertake.
Thanks for your online tutorial and excellent repair guides.