Backlit keyboard not working

[NiCk-]

Hey guys, my backlit keyboard has stopped working lately .. The "F5" and "F6" keys don't work .. I've tried resetting the SMC, unchecked "adjust brightness in low conditions" in the keyboard preferences, verified permissions and disk and even did a hardware test to see if there is a problem with the ambient light sensor but everything is OK ..

However, my keyboard won't turn on .. Any ideas ???? I think that this may be a software problem and that is why I'm posting here ..

EDIT: I have attached an image of the "F5" and "F6" keys when pressed ..

 

[CoastalOR]

At first I thought it might be a hardware problem, but your attached picture changed my mind. Now I'm thinking corrupted OS that could require an OS reinstall.

Just for a test, lets try a few things to see what happens:
Hold the Option (alt) key and press F5. This should open the Keyboard System Preference.
Hold the Option (alt) key and press F6. This should also open the Keyboard System Preference.

While the keyboard preference is open:
Select the Keyboard button.
Select/Check the "Use all F1, F2, etc. keys as standard function keys"
Hold the fn key and press F6. This is now supposed to increase brightness.
Hold the fn key and press F5. This is now supposed to decrease brightness.

Tests are over. Restore normal settings. Deselect/Uncheck "Use all F1, F2, etc. keys as standard function keys" in the Keyboard Preference. Close Preference window and post your results.

 

[NiCk-]

At first I thought it might be a hardware problem, but your attached picture changed my mind. Now I'm thinking corrupted OS that could require an OS reinstall.

Just for a test, lets try a few things to see what happens:
Hold the Option (alt) key and press F5. This should open the Keyboard System Preference.
Hold the Option (alt) key and press F6. This should also open the Keyboard System Preference.

While the keyboard preference is open:
Select the Keyboard button.
Select/Check the "Use all F1, F2, etc. keys as standard function keys"
Hold the fn key and press F6. This is now supposed to increase brightness.
Hold the fn key and press F5. This is now supposed to decrease brightness.

Tests are over. Restore normal settings. Deselect/Uncheck "Use all F1, F2, etc. keys as standard function keys" in the Keyboard Preference. Close Preference window and post your results.

The keys are working fine with or without the function key .. But the keyboard will not illuminate and I still get the same icon

 

[CoastalOR]

The keys are working fine with or without the function key .. But the keyboard will not illuminate and I still get the same icon

The only other things I can think of is to:
1. Use or create another User account, log in, then see if the brightness keys work.
2. EDIT: DO NOT DO THIS TEST. Boot up in Safe mode (hold the shift key down during start up). Review the linked Apple Support article. It is slow starting and finder response is slow but a lot of software is not loaded, be patient (also you will have to log in, no auto log in). Test F5 & F6.
3. Download EtreCheck (free), run it, copy the results and paste it in a post to see what software is loading.

If none of those help then the only other software step I know of is to reinstall Yosemite. Do you have a backup just in case?

 

[CoastalOR]

Update: DO NOT do the Safe Mode test. I just tried it and the keyboard light is disabled. Sorry for the bad advice, but I suspected there might be an issue which is why I ran a quick test.

 

[NiCk-]

Just wanted to say that I've just clean installed El Capitan and my backlit keyboard is working perfectly ! The keys are fully functional now .. So, it was most definitely a software problem with Yosemite !

 

[vexorg]

It works in yosemite for me. It does disable itself if there is background is bright enough. Cover the camera and check it - for anyone else thinking the same.

 

[CoastalOR]

Just wanted to say that I've just clean installed El Capitan and my backlit keyboard is working perfectly ! The keys are fully functional now .. So, it was most definitely a software problem with Yosemite !

That is good news that the clean install of El Capitan solved your problem.

 

[NiCk-]

It works in yosemite for me. It does disable itself if there is background is bright enough. Cover the camera and check it - for anyone else thinking the same.

I did that and it didn't work .. I don't know what, but something went wrong in the settings and that made the ambient light sensor unusable .. I checked on the internet and I'm not the only one with this problem .. Because El Cap came out I thought of doing a fresh install for my 2012 rMBP .. That fixed everything so it is obvious that it was a software related and not a hardware related problem .. However, one should not go through all that just to illuminate his keyboard

That is good news that the clean install of El Capitan solved your problem.

Thanks for all your help ! I did try out some things but because I was very busy lately I never had the chance to answer !