Hi all,
So I picked up a bit of a project 2008 G37s Coupe (5AT) a little while ago...
The other day, as I was parking, the car started to make a terrible clacking sound similar to that of a diesel. I looked at the dash and boom... check engine light is on
Some factors that are important to this:

1) I think the ground points are pretty corroded, I will be cleaning those up soon. I suspect that's why the driver's door switch works kind of erratically right now. Maybe that messed up a VVEL solenoid or something? Why is my CEL still on?
2) I was planning on getting a video of the sound but after I let the car cool off a bit (I've been babying it since I don't know a ton about it yet fyi) it didn't happen again. I didn't want to cause any further damage so I haven't turned it on since.
3) Check engine light was still on upon the second fire-up where it didn't make any bad sound

I was not able to get a video of it happening, but here is a clip I found of almost the exact same thing:
https://youtu.be/A-K26tb_TFw

Any thoughts?