Your gain/loss basis would be $12,500 and the depreciation that needs to be entered is $12,500 (don't enter an amount larger than your original Basis). It should show a gain of $3600 (the total sales price).
If the program is not cooperating with that, you can either (a) wait until TurboTax fixes it or (b) say you converted the vehicle to personal use, then report the sale in the "Sale of Business Property" section.
