I've been trying to figure out what parts I'm finding on my garage floor. I found a plug that was about half an inch across at the head about about a half an inch long, like a plastic bolt. It was dirty, and it had "Nissan" and "M12" on the top of it. Today, I found another one on the floor. Does anyone know what these plugs are, or where they go? It looks like it's an outside part, from the dirt on both. I haven't had time to crawl under the truck to figure out where these are coming from. Anyone else seeing this?