I have a 2014 Prius. Both of my taillights are out but the break lights still work, is my only option to replace the tail light assembly or is their something else I should try first?
First step is removing the bulb and inspecting the filament to see if that's the problem. Of course I've only worked on tailights of one Gen3 Prius, and maybe your tailights are LED? IF that's the case the problem is elsewhere in the wiring or fuse, not in the bulb. Pretty sure your owner's manual will give you info on how to replace the bulb if it's not LED.
If both are out, wouldnt you think maybe it is not the bulbs themselves, but the wire harness or a fuse?? Just a thought I would test the wire with a multimeter and see if you get any voltage readings as you turn it on and off. Then test or visually inspect the fuses. Also you can visually inspect the bulb. A dead one will have the small little wire inside fried and cut in half. Im sure your bulbs are fine though
Depends on how long it took them to notice the first light was out... It it wen't on for months and they didn't know, then maybe the other bulb went out because both bulbs are the often the same age? But the main reason I say check the bulb is because that takes the least amount of physical effort.
The first thing I would think of is: Is the headlight switch set to DRL instead of ON ? Are the headlights automatic and it is daylight out ?? If none of that applies, maybe there is a loose or broken ground.