My car expenses were significantly less than the amount in Box 14

That may be.  However, if you submitted mileage to your company, then you can be reimbursed up to 54.5 cents per mile for the business use of your car.  It's one of the few generous spots of the tax code, because very few people spend 54.5 cents/mile on their car expenses, so a good chunk of the reimbursement ends up being "tax-free" money.  It is why an accountable plan is so beneficial:  the money you receive is tax-free, whereas the company still gets the business expense for reimbursing you.  Because of tax law changes through the Tax Cuts and Jobs Act, deducting these expenses on the tax return is no longer an option, so an accountable plan is a significantly better way to account for these expenses.  Double-check with your payroll company if you wish, but your W-2 doesn't sound like any additional entries are needed.

My apologies for not getting all the details into my initial question. I appreciate your answers! I do receive  a 14 cents per mile reimbursement as I accrue the miles; which, like my other travel expenses, doesn't show on my W2. So this amount in Box 14 is in addition to the mileage reimbursement

Box 14 is informational.  It is showing that you received a non-taxable reimbursement for that expense because you submitted it to a qualified accountable plan.  You should enter the information into box 14 on the W2 screen as it appears on your W2 (in the dropdown box you can scroll all the way down to the last option and select "Other").  It should have no impact on your actual tax return, however.