TurboTax did not prepare your tax return. You prepared your tax return yourself, using TurboTax as a tool. The error in your tax return could have been caused by a calculation error in TurboTax, or by an error in the information that you entered.
TurboTax will not pay the tax that you legitimately owe. If your tax return had been correct, you would have paid the additional tax when you filed. If the error was caused by a calculation error in TurboTax, TurboTax will reimburse you for the interest and penalties that you pay, under its 100% Accurate Calculation Guarantee. Go to the link that tagteam posted above for instructions to submit a claim for reimbursement.
One other possibility, though less likely, is that the state is wrong. Review the billing notice carefully and make sure it's correct before you pay the amount due or file an Accuracy Guarantee claim.
