In most states, a creditor who has followed the proper procedures for repossession and sale is allowed to sue you for a deficiency judgment to collect the remaining amount owed on your credit or lease contract.
Depending on your state's law and other factors, if you are sued for a deficiency judgment, you should be notified of the date of the court hearing. This may be your only opportunity to present any legal defense.
If your creditor breached the peace when seizing the vehicle or failed to sell the car in a commercially reasonable manner, you may have a legal defense against a deficiency judgment. An attorney will be able to tell you whether you have grounds to contest a deficiency judgment.