70 step side back up lights ground?
 

I recently replaced both my back up lights because neither worked. Now one side works and the other still doesn't. I have confirmed it must be a bad ground on the one not working because when I ran a jumper wire to the mounting bolts for the housing, the light works. So, my question is, where does a stepside backup light get it's ground from?

Re: 70 step side back up lights ground?
 

If one wire, thru the outer socket to the bumper to the frame.