when I lock, or unlock the doors, the headlights go up & down, and the passenger side buzzes for several second??https://www.gmforum.com/gm/images/smilies/confused.gif

the only things i can think of are something on the door switch is causing interference with the headlight motors, through the park lamp circuit which powers the interior button lights as well as a signal to the headlight opener control module. or there are wires chafed together at one of the fuse boxes.

Or back feed through a bad ground?

have you checked body control module? on some cars it have certain control authority over those things

the diagrams dont show any connection to the bcm for the lights on this car