Have you already e-filed your return? If so, then you will not be able to change your bank details. You will have to wait to see if your tax return is accepted or rejected by the IRS.
If the return is rejected, then you can update your information and resubmit your return. Should the tax return be accepted and the IRS (and State, if any) cannot deposit your refund to your account, then a paper check will be mailed to you.
You can refer to this TurboTax FAQ for complete information:
Once your return has been accepted (or mailed), it's too late to change your bank account for direct deposit.
If you haven't filed yet, you can still change your bank account info for direct deposit.
If the info you provided is for a closed or invalid account, the government will mail you a refund check.
If the info you entered is someone else's account, don't worry – some banks won't deposit tax refunds into accounts where names don't match up. The best way for you to track your federal refund is to call the IRS at 1-800-829-1040.
If your recently-filed return is in pending status, wait until it's either accepted or rejected.
If rejected, you can update your account and any issues that caused the rejection. Open your return in TurboTax and go through the File section again to update your bank account before re-submitting your return.
If accepted, you'll get your refund check in the mail.