My 2011 GMC Terrain has had this problem only a handful of times since I have owned it. Its the noisy rattle on startup that last for 3 seconds. You can see a video on YouTubeThis is EXACTLY the sound my Terrain is making. It honestly has only done this maybe 5 times in 4 years that I have owned it. It only seems to happen if the Terrain sits for a day or more with out being started. Since I am following quarantine and my terrain is now sitting for sometimes days with out being started I am noticing it more often. After researching I found that it is a known problem, the bulletin number is PI0562F. It recommends replacing both camshaft position actuators and solenoids. Replacing the actuators is too complicated of a job for me, but just replacing the solenoids is easy. Do you think just replacing the solenoids could fix this issue?