I drive '07 Sierra, new body style and I'm having an issue with the turn signals. They both blink fas like a bulb is out. I've checked all the bulbs myself, including the sidermaeker lamps in the headlight assembly. Those were blown, so I replaced them. Still no dice. Furthermore, they don't light up even with new bulbs. I pulled them again and checked them and I didn't blow the new bulbs. I put a multimeter in the socket and no juice. My thought is maybe it's a grounding issue? I don't really know though. Or even where to look if this is the case. This is a little beyond my scope of knowledge.