Prius headlights work only on highbeam - 2006 Toyota Prius

There should be separate fuses for high and low beams on a Prius. If one of your headlight bulbs is bad, it could have blown the low-beam fuse. Check for blown fuses behind driver's side headlight fuse panel. If new one blows, replace headlight bulbs and try again.

On 2004-2009 Prius, driver's side headlamp bulb can be replaced by removing hold down screws and folding fuse panel upward to access rear of headlight assembly. Large round cover with 3 tabs unscrews about 1/4 turn to remove. It's really tight and held by friction of large O-ring so it'll take some muscle but it will eventually give. Be careful replacing bulbs as metal clips can be easily installed incorrectly resulting in tilted headlight beam. 3-tabs must rest on flat surfaces on mounting area before spring clip can be latched in place. 3-prong plug can be wiggles sideways/up and down to remove from bulb.