40 CFR 90.121 - Certification procedure - recordkeeping.
(a) The engine manufacturer must maintain the following adequately organized records:
(1) Copies of all applications filed with the Administrator;
(2) A copy of all data obtained through the in-use testing program; and
(i) A description of the test engine's construction, including a general description of the origin and buildup of the engine, steps taken to insure that it is representative of production engines, description of components specially built for the test engine, and the origin and description of all emission-related components;
(iii) A description of all maintenance, including modifications, parts changes, and other servicing performed, and the date(s), and reason(s) for such maintenance;
(iv) A description of all emission tests performed including routine and standard test documentation, as specified in subpart E of this part, date(s), and the purpose of each test;
(v) A description of all tests performed to diagnose engine or emission control performance, giving the date and time of each and the reason(s) for the test; and
(vi) A description of any significant event(s) affecting the engine during the period covered by the history of the test engine but not described by an entry under one of the previous paragraphs of this section.
(b) Routine emission test data, such as those reporting test cell temperature and relative humidity at start and finish of test and raw emission results from each mode or test phase, must be retained for a period of one year after issuance of all certificates of conformity to which they relate. All other information specified in paragraph (a) of this section must be retained for a period of eight years after issuance of all certificates of conformity to which they relate.