Section 85.1901 - Applicability(a) The requirements of this subpart shall be applicable to all 1972 and later model year motor vehicles and motor vehicle engines, except that the provisions of 40 CFR 1068.501 apply instead for heavy-duty motor vehicle engines and heavy-duty motor vehicles certified under 40 CFR part 86, subpart A, or 40 CFR part 1036 or 1037 starting January 1, 2018.(b) The requirement to report emission-related defects affecting a given class or category of vehicles or engines shall remain applicable for five years from the end of the model year in which such vehicles or engines were manufactured. 81 FR 73972 , Oct. 25, 2016, as amended at 88 FR 4472 , Jan. 24, 2023 81 FR 73972 , 12/27/2016; 88 FR 4472 , 3/27/2023