Help! What is this? (found under car)

It's a hole plug.
Nothing to worry about.

 

There are typically two plugs to be attached by the dealer during their Pre-Delivery Inspection (PDI). There should be another one on either the left or right side of the underbody between the front and back doors. Simple enough to replace.

 

Sometimes. Other times, they are just there for "looks".
And that one looks pretty pristine. So it might be an "extra" left over from the last service visit OR from the factory.

Either way.......it is highly unlikely that whatever hole might be left open will cause any real problem over the course of any reasonable lifetime of the vehicle.

BUT......by all means, if it worries the owner, try to inspect the whole vehicle to find out where it came from.
And if that fails, PAY a shop to put it up on a rack and do a better inspection.
And when neither of those things is able to find where it came from.......then have nightmares and loose sleep over it.
Consider trading the vehicle in so you can regain your piece of mind.

 

I can't think of a single good reason for a but hole plug on any vehicle

 

It’s there for a reason.

There’s 2 in the hatch one under the spare tire and One in the bottom of the battery well. Which is handy because A G2 leaks like a sieve.

Take the hatch apart take the spare tire out and get a flashlight and look in the bottom of the well the 12 volt battery sits in its full of water.
Or not.... see which are side is missing that plug, if the car lives outside no garage your u need those plugs installed as mice I’ll get in the car and tear it up.
In fact check the cabin filter it may show mice activity if so check the Engine air filter box

 

They are both quite simple and no tools required, so no screws to remove. Google it, or search the Gen 2 forums here. It's been discussed many times.

 

if You have a leak there’s water in the battery well.