Hello -
If you contributed to a 401K through your employer you would see your contribution made to your 401K on your W2 in Box 12. Please confirm the entries you made in Turbo Tax from your W2 for box 12 as seen on your W2.
If you 401K contribution was made through your employer, remove the IRA contribution from where you previously entered it. If you did not make a 401K contribute through your employer and box 12 on your W2 does not list any IRA Contributions, I would need more information as to the type contribution you made.