Chosen Solution
On my S4 SPH-L720, the back button to the right of the home button will not light up. It still functions, just no illumination. The menu button on the left side of the home button still illuminates so I don’t believe this to be a software issue. What assembly is the actual light on? Home button flex cable, display assembly, midframe? I’m trying to determine if this is an easy fix or worth the hassle.
Not worth fixing. You’ll need a replacement screen to fix this. The home button back and recent cable assembly goes between the screen frame and glass which would require separating the glass which most likely results in breaking a LCD.
