I only found the thread . . . I do not have a 990.
After reading to the end . . . Better contact your dealer . . . It does not work for everyone.
End of thread:
Mine is a 2010 990. The referenced instructions did not work. My new HID bulbs arrived, so I'm ready to put it back together. Not knowing what the brown/black wire does, I'll have to solder it back together & button things up.
Edit: Google search shows that others are still struggling with this issue. I'm going to call my expert dealer tomorrow and see if he has any tips. Some of the instructions state to press both buttons while in trip F. I can't seem to get back to trip F now. Puzzled.....