All withdrawals from a pre-tax 401k are always subject to regular income tax, plus a 10% penalty if you are under age 59-1/2. There are no exceptions to the income tax and debt is not an exception to the penalty. Depending on how much you withdraw and what state you live in, taxes and penalties can eat up as much as 50% of the withdrawal.
If you can't pay your federal taxes owed, you can request a payment plan. You want to do this directly on the IRS web site--trying to set up a payment plan using Turbotax is not effective for several reasons. If you are just filing your taxes now, tell Turbotax you will pay by mail. Make as large a tax payment as you can electronically at www.irs.gov/payments (paying more now will reduce the interest and penalties you will be assessed on the balance due).
Then go to the IRS web site and request a payment plan. There is a non-refundable application fee.
https://www.irs.gov/payments/payment-plans-installment-agreements
