Trailblazer and lights dimming and brightening

Trailblazer lights dimming and brighteningmy dealer
said it was the sensor for the automatic lights in and
that GM and Chevy have not come up with any fix
for it or A way to replace it so there  was nothing
they could do .  I believed that he was lying and
screwed me over until I read forum after forum of
people complaining of the same thing so who
knows he could be telling the truth... Anybody else
have an answer for this or a fix?