Dell E5530 Backlit Keyboard not adjustable

I have a Dell Lattitude E5530. PROBLEM: keyboard backlight is always on and very dimmed. I cannot change the brightness: the bios settings (disabled, 25%, 50%, 75% 100%) do not change a thing. Also, the fn + right arrow combo shows the icons change (have installed Dell Feature Enhancement Pack), but no change in keyboard backlight brightness. Keyboard: Chicony P/N: MP-10H23USJ886. DP/N: 0HG3G3. MP-10H2. Installed: Latest Bios BIOS, non-vPro supported (Broadcom TruManage), A13. Latest Dell drivers, Latest Windows drivers. I dont know what the problem can be. Even the bios settings do not change the brightness. I looked at how the keyboard cable was connected, and that seems ok. Any ideas?