I have a 2015 automatic with 30000 miles on her. I got the car only having 7 miles and all was quiet until it hit about 21000 miles. That's when a tapping noise started. At first I flipped out because I thought I blew the motor up. But I started searching and listening. I pinpointed where the tapping was coming from. At the back of the motor in the middle around the upper section there is a little black box. This box has a small line coming out both sides. Someone made the comment to me about being part of the fuel system??? But I can not seam to find out what this box/part is called or what it is actually for. This box is what is tapping under the hood of my Cruze and I need to fix it. It honestly hasn't seam to affect my car in any way. That I have noticed anyways! But I know it's not normal. This noise was not there at first and now all a sudden is. And it is a constant tap. Doesn't go away when the car warms up. It's all the time. I have had every oil change and maintenance done when due. And even taking the car in not one mechanic has asked it said anything about it. And I asked one guy at the dealer what the box was and he said he wasn't sure and that I would have to put us in maintenance repair to have the mechanics tell me what it is!!! Can someone tell me what this box/part is called and what it is for?