The IRA Contribution Worksheet does not apply unless the contribution was a personal contribution to an IRA. A 401(k) is not an IRA. It's certainly possible to have someone or some entity make a deposit into an IRA on your behalf, like direct deposit of your pay, but it would not be a contribution to an employer plan.
The Keogh, SEP and SIMPLE Contribution Worksheet applies and gets its input from the K-1 Additional Info for a box 13 code R entry and from Schedule SE in response to the box 14 code A entry. In the absence of the box 13 code R entry you can get the same result by entering the 401(k) contributions in the Self-employed Retirement section of TurboTax, but the contribution is still only appropriate if the 401(k) is established under the partnership (in which case it should be shown with code R in box 13).
