Screen Backlight and Keyboard Backlight not working

Today I went to power on my MacBook Pro Retina 13” Late 2013 discovering that both the keyboard and screen backlights are not working (I noticed that by putting a light behind the apple logo and I saw a picture on the screen, confirming that the mac is working).

I have tried to reset the PRAM, SMC and i even tried Apple Diagnose, which didn’t show that there are any problems with the screen or the keyboard.

i have tried to turn off the automatic brightness but didn’t work either.

So is this an hardware or software problem? How can I fix it and what do I need to replace?

edit: if this can help you determine the problem, about three years ago I replaced the battery and this computer is used and stored in a quite cold enviroment all the time.