If the second mortgage was a non-recourse loan used for the purchase of the home, then it should say the debtor is not liable for repayment of the loan in box 5 of your 1099-C. If this is the case, TurboTax will automatically remove the forgiven debt as income on your tax form.
If it doesn't, but instead says you are liable for the debt in box 5, you'll likely have to call the lender to have them look into it and potentially reissue a 1099-C with the correct information; otherwise, the IRS will assume you owe taxes on the forgiven debt.
