In many jurisdictions, the lienholder (in this case, you) has the right to repossess the vehicle if the borrower (in this case, your ex) fails to make payments as agreed upon in the loan agreement. However, the lienholder must generally follow certain legal procedures, such as providing notice to the borrower before repossessing the vehicle.
The exact procedures for repossessing a vehicle vary by state, so it is important to follow the specific laws and procedures in your area. In some jurisdictions, the lienholder may be required to obtain a court order before repossessing the vehicle, while in other jurisdictions, the lienholder may be able to repossess the vehicle without a court order, as long as they follow certain procedures, such as giving notice to the borrower and/or filing certain documents with the local motor vehicle department.