There are two questions to think about.
The first is - who owns the car on the facts? That is, who is the registered owner?
If that isn't you, then being the borrower doesn't really give you much basis to just take possession of the car.
(the borrower probably has what lawyers call "an equitable interest" in the car, but that
does not always and automatically give them an a right to possession).
The second question is - who borrowed the money and/or is responsible for repaying the loan?
That borrower will need to keep paying, no matter where the car is, no matter who the registered owner is,
and no matter where the car lives. You also need to know if the loan is secured (by the car, or by something else), or is unsecured. This will be in the loan papers, or you (the borrower) can just ring the lender and ask.
Unless you/the borrower/whoever is/are "behind on payments"
(lawyers, accountants, and bankers, talk about a loan being "in arrears"),
then forget the credit rating thing.
Unless you are already a financial train wreck, that is the least of your worries.
I strongly recommend an early conversation with the lender.
If at all possible, make an appointment to see a manager-level real person
in an actual branch or office.
As a general thing, lenders would much rather do a bit of re-arranging,
than have to deal with a loan gone bad.
Remember - this set of facts may be new, and difficult, and maybe even embarrassing, to you,
but the lender has probably seen this sort of thing before.