Only the business portion of the vehicle would have been deductible for active businesses.
The portion of the car used for personal use is taxable if there is a gain, but not deductible if it is a loss. From what you are describing, it would appear this loss is not deductible.
For more information, see: How do I edit or delete sale of business property (Form 4797)?
Vehicle Sale with business and personal use question answered.
