Comment 98 for bug 1510344

This issue affected me with a new Dell E5470 on 14.04

The issue would go away with a factory reset but after doing updates it would reappear.

The way I eventually got it fixed was

Step 1: as stated above

Edit file
/etc/dbus-1/system.d/org.freedesktop.UPower.conf

change:
    <allow send_destination="org.freedesktop.UPower"
           send_interface="org.freedesktop.UPower.KbdBacklight"/>
to:
    <deny send_destination="org.freedesktop.UPower"
           send_interface="org.freedesktop.UPower.KbdBacklight"/>

Step 2: Bios

In my bios file I had to find the settings for the keyboard timeout and change it to something else. So if it was set to 5 seconds then I had to change it to 10 seconds. If it was set to 10 seconds then I had to change it to 5 seconds.

Once I rebooted my system the keyboard returned to the expected behavior.