The complaint alleges that Detroit Diesel commenced construction of the engines during model year 2009, but did not complete construction of the engines until model year 2010. Because Detroit Diesel completed all manufacturing and assembling processes for the engines in 2010, the complaint alleges that the engines were produced in 2010 and required a certificate of conformity demonstrating compliance with 2010 emission standards. From approximately Jan. 5, 2010, through approximately June 1, 2010, Detroit Diesel sold the engines for on-highway use in heavy duty vehicles. Because the engines were not certified to the stringent 2010 NO x emission standards, Detroit Diesel's introduction of these engines resulted in excess emissions. The engines were manufactured in Detroit, Michigan, but were introduced into commerce across the country.