I'm assuming you don't have the title, because if you did, the lienholder's interest should be signed off. Look at the "Requirements after paying off your car loan" section of
this page. There's a link to the lenders that shows Conseco Financial Services successor as Greentree Financial Services at (800) 426-4433. I think you need a "Lien Satisfied" document from them. If they can't provide one, I think the DMV has a mechanism where you can post a bond.