iPhone 6s backlight not working

I repaired the backlight replacing FL4211, initially everything worked fine ... but at the time of closing the device did not start anymore 'and itunes gave me this error 0 × E8000015 then I put in dfu restoring solve the startup problem but I do not see again nothing on the display.

Check again resistance on lcd connector, backlight voltages, diode, everything ok ..

Now I wonder what could have happened .....

If the backlight circuit is ok, then what could be blackscreen ???

I state that (to finish earlier) I was wrong to work on the card inserted in the body