I see this is a very old email string but people are still posting to it so I'm going to share my story. In December 2020 I purchased a P53 laptop with a backlight keyboard. Unlike many of the people who have posted on this subject, I didn't have any problems figuring out how to turn my backlight off/on. I have a model that uses the Fn+Spacebar. The reason I found this email string was because I felt that the backlight was not bright enough. It has three levels of control: low, brighter and off. I have now determined that the light is actually plenty bright at the highest sitting but the white translucent material used for making the keys to form the letters/numbers/symbols is too opaque to let much light through, at least, when compared to other laptops that I own. But, I have now determined that I will just have to get use to fact that the ThinkPad keyboard will have "dimmer" letters/numbers and symbols than my previous laptops.
However, if you are like me - it drove me crazy that I had to constantly press the Fn+Spacebar to turn the backlight back on after the computer goes into sleep mode. I know this is a small thing but it gets annoying (at least for me) after doing it a 100 times in a day! Especially, since I know it doesn't have to be this way. My old HP laptop that I replaced with my new P53 did not have this issue. If the HP went to sleep ... just a touch to the keyboard or the mouse/touch pad, woke up the computer and the backlight came back on, if it was previously on. I searched and searched the internet looking for way to change the default behavior of the backlight of my new ThinkPad and finally found a solution. I found a reference to a program that someone had created to solve the problem called: LBC Service Settings
If you are interested in controlling whether the backlight comes back on "automatically" after the computer goes into sleep mode, check out this program. It was not written for my specific computer model but it was written for a ThinkPad that uses the key combination Fn+Spacebar which mine uses so I took a chance. I downloaded the program and installed it and it has worked flawlessly for me for two months. I am no longer annoyed by having to press the Fn+Spacebar a 100 times a day! I'm leery of downloading unknown programs over the internet but I took the chance on this one and I'm glad I did. I love that I now have control over the default behavior of the backlight on my P53 ThinkPad. My spyware/malware software has not reported any issues with the program but you will need to use it at your own risk. See link below:
https://github.com/JooJooBee666/LBCService
For those who are not familiar with the GITHUB.COM site it is a place where 1,000's of programmers share "open source" free software that they have created.