Updating my own post: Google showed me how to test relays, and the wiring diagram on this site showed me which ones to check. That'll be my next plan of attack.

I'd appreciate advice on troubleshooting my low beam failure. A week ago the left headlight on my '03 XC90 went out. Thinking it was the bulb, I got a new one but it didn't work. Yesterday, my right headlight went out. My high beams don't work, nor do my DTR's. My fog lights and turn signals work. T...