(a) A selective enforcement audit for axles or transmissions would consist of performing measurements with a production axle or transmission to determine mean power loss values as declared for GEM simulations, and running GEM over one or more applicable duty cycles based on those measured values. The axle or transmission is considered passing for a given configuration if the new modeled emission result for every applicable duty cycle is at or below the modeled emission result corresponding to the declared GEM inputs.

(b) Run GEM for each applicable vehicle configuration identified in 40 CFR 1036.540 using the applicable default engine map defined in appendix C of 40 CFR part 1036, and the default torque curve given in Table 1 of this section for the vehicle class as defined in § 1037.140(g). For axle testing, this may require omitting several vehicle configurations based on selecting axle ratios that correspond to the tested axle. For transmission testing, use the test transmission's gear ratios in place of the gear ratios defined in 40 CFR 1036.540. The GEM result for each vehicle configuration counts as a separate test for determining whether the family passes the audit.

(c) If the initial axle or transmission passes, the family passes and no further testing is required. If the initial axle or transmission does not pass, select two additional production axles or transmissions, as applicable, to perform additional tests. Note that these could be different axle and transmission configurations within the family. These become official test results for the family. Use good engineering judgment to use the results of these tests to update the declared maps for the axle or transmission family. For example, if you fail the audit test for any of the axles or transmissions tested, the audit result becomes the declared map. This may also require revising any analytically derived maps.