(a) The selective enforcement auditing program described in 40 CFR part 1068, subpart E, applies for all heavy-duty engines as described in this section. In addition, the provisions of 40 CFR 1068.10 and 1068.20 apply for any selective enforcement audits of these engines.

(b) For heavy-duty engines, the prescribed test procedure is the Federal Test Procedure as described in subparts I, N, and P of this part (including provisions of 40 CFR part 1065 as specified in this part), except that they shall not be subject to the test procedures specified in §§ 86.1360(b)(2) and (f), 86.1370, 86.1372, and 86.1380. The Administrator may, on the basis of a written application by a manufacturer, approve optional test procedures other than those in subparts I, N, and P of this part for any heavy-duty vehicle which is not susceptible to satisfactory testing using the procedures in subparts I, N, and P of this part.