the light housingwill create its own ground...just did a similar operation last night,
one wire and everything works fine

Bill

 

On the fog's it a 2 wire deal. I white, 1 Black to the lamp itself. On another note, the Grey wire I was going to use didn't work out. I tested itwith one light before Idressedup the wiring and everything was ok, plugged in the other light and snap goes the fuses in the fog light harness. No more time for that tonight, my honey got a new outfit from my second favorite store, Victoria's Secret,and its play time.

 

Well after all the bull crap I went through, tons of fuses, hours of removing wiring and re-installing. I finally got everything working perfectly. As it turns out, the fixture I got from HD was BAD!!! It had some kind of +voltage leak and was shorting itself out. Went to the dealer and they handed me a new one, no questions asked.