(a) Maximum Manufacturer Costs.—A standard under section 33102 or 33103 of this title may not impose—

(1) on a manufacturer of motor vehicles, compliance costs of more than $15 a motor vehicle; or

(2) on a manufacturer of major replacement parts, compliance costs for each part of more than the reasonable amount (but less than $15) that the Secretary of Transportation specifies in the standard.

(b) Costs Involved in Engines and Transmissions.—For a manufacturer engaged in identifying engines or transmissions on October 25, 1984, in a way that substantially complies with the standard—

(1) the costs of identifying engines and transmissions may not be considered in calculating the manufacturer's costs under subsection (a) of this section; and

(2) the manufacturer may not be required under the standard to conform to any identification system for engines and transmissions that imposes greater costs on the manufacturer than are incurred under the identification system used by the manufacturer on October 25, 1984.

(c) Cost Adjustments.—(1) In this subsection—

(A) "base period" means calendar year 1984.

(B) "price index" means the average over a calendar year of the Consumer Price Index (all items—United States city average) published monthly by the Secretary of Labor.

(2) At the beginning of each calendar year, as necessary data become available from the Bureau of Labor Statistics, the Secretary of Labor shall certify to the Secretary of Transportation and publish in the Federal Register the percentage difference between the price index for the 12 months before the beginning of the calendar year and the price index for the base period. For model years beginning in that calendar year, the amounts specified in subsection (a) of this section shall be adjusted by the percentage difference.