As Kris mentioned, TurboTax is not set up to report the sale of an asset or vehicle that has varied in business percentage from year to year. You can NOT report it in the vehicle section (well, unless you really know how to manipulate the numbers).
You would need to MANUALLY calculate things and report it in the "Sale of Business Property" section.
In the event the vehicle was originally a personal-only vehicle then converted to business use, it gets even more complicated and I would highly recommend going to a good tax professional.
