08 Chevy 2500hd low Beams not working

My low Beams don’t work.  High beams do
and all running lights work.  I’ve checked the
fuses and they’re all working.   I replaced the
relay and the low beams still don’t work.  I
have a new switch coming and I’m hoping
that solves the problem.   What else could be
wrong and does any me have a wiring
diagram i could use to trace the system I’d the
switch isn’t the problem?