The vehicle is a 2003 Chevrolet Trailblazer. The low beams aren't working. High beams are. The fuse is perfectly fine (tested and swapped out). The bulbs are fine too.

A mechanic told me it could be the "body modulator". I've never heard of this before. Could this be the problem? If so, how hard is it to change out for a shade tree mechanic?

If not, what else could this be?