After a car has been repossessed and auctioned off what are the consumer's rights regarding payment of the negative balance owed after the vehicle is auctioned?

Very simple really,you have the right to pay it. If you don't pay it, the lender will likely seek a judgment against you. If successful, they will proceed with any other legal remedies available to collect. Those include garnishemnt of your wages, lien against other property you own, etc. You can make an offer to settle, they can refuse or settle. Last but not least, you can do the bankruptcy deal. Try your best to avoid this. It will haunt you for 7-10 yrs. Good Luck