Deductions & credits

First you need to follow the steps to simply remove your vehicle from service.  Add the new vehicle as a separate asset like it has nothing to do with the vehicle you traded.

I would suggest you select it was sold/disposed of and then enter the date removed from service.  Take down all of the prior depreciation for the vehicle and the current amount. Indicate that it was not sold, simply removed from service. If you used the standard mileage rate instead of actual expenses see the chart below to figure out the depreciation on the vehicle for all years using the business mileage for each year.

1. Add the percentage of business use for each year together for the life of the asset (from first year and every year you used it for business before trading it). Or take down all business miles for all years. 
2. Take the total business miles divided by the total miles (all years both businesses) for the actual business use percentage.
3. Multiply that percentage by the original full cost of the vehicle. This is the business portion of the original cost basis for the vehicle. 
4. Write down the total depreciation expense for all years.  This is the total depreciation used on the vehicle. (actual or standard mileage portion)
5. Now you are ready to enter the sale of the vehicle under Sale of Business Property (not the business activities).

To record the sale of a business asset (vehicle) outside of the business/asset entry.

1. Sign into your TurboTax account:
   1. Select that you disposed of the asset and answer the questions as though it was disposed of
   1. Under Wages & Income >Other Business Situations > Sale of Business Property >Start or Revisit > Enter your sale
   2. See the images below for assistance.

Please update the issue if you need further clarification.