While you don’t necessarily have the same rights to the vehicle as the primary borrower, you – as the co-signer – are equally responsible for ensuring the loan is paid back.
If the primary borrower doesn’t make their monthly loan payment, you will be asked to make the payment. Any missed payments could also appear on your credit reports and impact your credit scores, making it harder for you to get credit in the future.
Defaulting on a loan could also lead to the lender repossessing and selling the vehicle, and depending on state law, the lender could sue you and the primary borrower for the outstanding loan balance.