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2015 Sierra 1500. Just ran into the same issue, we went to see a late movie last night, when I started to drive home I noticed it was so dark so I pulled over and sure enough, both headlights were out. I pulled the driver side bulb and it was fine, not burned out and today I tested the plug and it was showing 6v, yet no light. My first instinct was the BCM but no one had one in stock so instead of doing nothing, I figured it has 70k miles and a new set of bulbs couldn't hurt. Once I removed the air box and got to the passenger bulb I noticed the filament was gone, burned out. I did that one first since it's kind of a pain to get to. So....both had voltage yet the good bulb still did not work, yet replacing the bad one made them both work. I don't understand how that is possible but, this was exactly the case... I tested everything twice to ensure I wasn't losing my mind. Perhaps the good one only had voltage without a bulb in it is the only logical thing I can think of although I don't see how that's possible either, maybe the BCM just gets confused? It still confuses me lol. Spend 60 bucks on some LED's and save yourself the trouble and headache.