Fund Change Notice Requirement

Is there a 30-day notice requirement for simply adding a new fund to a 401(k) lineup, not mapping any assets to it? 

Generally, yes, see 2550.404a-5 (c). 

https://www.law.cornell.edu/cfr/text/29/2550.404a-5 

(c)Disclosure of plan-related information. A plan administrator (or person designated by the plan administrator to act on its behalf) shall provide to each participant or beneficiary the plan-related information described in paragraphs (c)(1) through (4) of this section, based on the latest information available to the plan.

(1)General.

(i) On or before the date on which a participant or beneficiary can first direct his or her investments and at least annually thereafter:

(A) An explanation of the circumstances under which participants and beneficiaries may give investment instructions;

(B) An explanation of any specified limitations on such instructions under the terms of the plan, including any restrictions on transfer to or from a designated investment alternative;

(C) A description of or reference to plan provisions relating to the exercise of voting, tender and similar rights appurtenant to an investment in a designated investment alternative as well as any restrictions on such rights;

(D) An identification of any designated investment alternatives offered under the plan;

(E) An identification of any designated investment managers; and

(F) A description of any “brokerage windows,” “self-directed brokerage accounts,” or similar plan arrangements that enable participants and beneficiaries to select investments beyond those designated by the plan.

(ii) If there is a change to the information described in paragraph (c)(1)(i)(A) through (F) of this section, each participant and beneficiary must be furnished a description of such change at least 30 days, but not more than 90 days, in advance of the effective date of such change, unless the inability to provide such advance notice is due to events that were unforeseeable or circumstances beyond the control of the plan administrator, in which case notice of such change must be furnished as soon as reasonably practicable.

Even if nothing in ERISA or other law requires such a notice to participants, a recordkeeper's or other service provider's agreement might set some notice to the service provider before it is obligated to perform its service about the added investment alternative.