TurboTax is not set up to report the sale of vehicles and other assets that have varied in business percentage from year to year.
In the vehicle section, you need to say it was converted to personal use. Then you report the sale in the "Sale of Business Property" section, using the MANUALLY calculated amounts that Mike outlined. However, reporting it in the section may cause other errors in some calculations (QBI, home office, and more), so going to a good tax professional might be your best option.
