This sucks: passenger light isn't lighting anymore. And as I am alone with my two young children sleeping in the house, I can't troobleshot right now. Anyway here's a pic with only one light.
If it's a harness setup, chances are it's a loose wire. When mine went it blew the fuse and both were out. I had to pull both ballasts to find the issue. Unless both headlights have their own fuse. Or it could be a bad igniter. Seen that happen too. Good luck with the trouble shooting!