My front driver's side turn signal works, but the "running light" does not - the yellow light on the "wraparound" part of the headlight. They are the same bulb.

What do you think the problem is? Are there multiple filaments in the same bulb, and one of them went out? Or could it be a bad connection in the socket the bulb plugs into? Something else?

 

I took the bulb and connector out and it appears the one bulb does indeed have two filaments. Neither looked obviously broken to me, but the bottom one worked for the turn signal and the top one did not for the running lights. So I'm going to go on the assumption that the top filament is blown and order a new bulb.

 

I ordered a new bulb and replaced the old one. At first, it did not work either. Then I turned it around (it goes into the connector slot both ways) and pushed it in a little tighter and it started working.

Solved!