You should consult with your Consignment Pro to get their specific answer to this question. However, it is usually okay as long as the amount you owe (bank payoff) is not significantly more than your vehicle's retail consignment value minus their consignment fee(s). Once your vehicle is sold, your Consignment Pro will pay your lienholder directly from the sale proceeds and give you a check for any difference. If you owe more than your vehicle's retail consignment value (called Negative Equity or Underwater), many Consignment Pros will still allow you to enroll in their program, but may require you to place the estimated difference/shortfall in escrow at time of enrollment.
You might be interested in reading: Underwater With a Negative Equity Car Loan? Discover a New Way to Get Your Head Above Water