The SD90MAC was introduced in 1995, along with the SD80MAC locomotives. The SD90MAC was designed to utilize the new 16-cylinder H-engine, while the SD80MAC was designed to use the 20-cylinder version of the existing 710G engine. However, technical problems with the engine resulted in the first locomotives being shipped with 16-cylinder 710G engines, making them similar to the SD70MAC's. These locomotives were given the informal model designation SD9043MAC by railroads that purchased them with the option to re-engine them with engines when they became available. This upgrade program, however, was never taken advantage of by SD90MAC buyers due to reliability issues with the newer engine. Over 400 SD90MAC locomotives fitted with the 710 engine were built.