Sale of company vehicle

Create an income account called gain/loss on asset sales.
Calculate and post partial year depreciation (if this asset is subject to depreciation).

Then journal entries

debit accumulated depreciation and credit gain loss for the amount in the accumulated depreciation account (if this asset is subject to depreciation)

debit gain loss and credit the fixed asset account for the total in the fixed asset account

Debit the loan if there is one for the balance, and credit the gain loss account

enter the payment for the sale as a deposit and use the gain loss account as the source account for the deposit

Enter the payment made as a debit to the gain loss account and use owner equity investment as the offsetting account

The "balance" was not the current value of the vehicle, only the outstanding loan liability.  This part is easy

Debit: Loan 18,750.63

Debit Interest: 79.37

Credit Vehicle Sale (income): 15,000.00 

Credit Owner Contribution (equity) 3,830

This is only the first half . Whatever your following numbers are will determine your loss or gain

Debit Accumulated Depreciation : however much was taken as depreciation over time in this vehicle

Credit: original cost

This recaptures your previous benefit of yearly depreciation expense. But you need two numbers. Original basis, accumulated depreciation.  To illustrate, I will pull two numbers out of thin air.

Assuming:

Original purchase price all in : $30,000

Owned for 4 years, depreciation taken 3.5 years straight line on 5 year property (first year is one half) = $21000

So 

Debit: Loan 18,750.63

Debit Interest: 79.37

Credit Vehicle Sale (income): 15,000.00 

Credit Owner Contribution (equity) 3,830

Debit Accum Deprec : $21000

Credit Vehicle Asset : $30,000

Debit: Vehicle Sale: $9,000

Drum roll...................final value in Vehicle Sale income is $6,000 which is ordinary income. There is a form for this and plug in your own numbers. For example, if you took a Section 179 full writeoff of vehicle then Accumulated Depreciation is equal to Cost basis and the entire $15,000 is ordinary income (payoff of loans never has an effect on P&L other than interest or other fees)