Quick question. On my gf's 09 Prius the warning button doesn't light up during the night with the headlights on. You can't see it. Is this normal?
if you mean the headlight indicator, no, it's not normal. if everything else is lit and the headlights work okay, perhaps you need a bulb.
there should be a picture of a light bulb looking like its lit (located to the right of the speedo near the center of the dash). when the brights are on you will get the little paw looking light close to the speedo. if it isnt lit im sure the bulb burnt out. but its a rather in depth procedure to get to it to replace it. from what i understand the entire upper dash has to be taken off to gain access to the light clusters