Detroit Diesel Corporation (DDC) is an American diesel engine manufacturer headquartered in Detroit, Michigan, United States. It is a subsidiary of Daimler Truck North America, which is itself a wholly owned subsidiary of the mulitinational Daimler Truck AG. The company manufactures heavy-duty engines and chassis components for the on-highway and vocational commercial truck markets. Detroit Diesel has built more than 5 million engines since 1938, more than 1 million of which are still in operation worldwide. Detroit Diesel's product line includes engines, axles, transmissions, and a Virtual Technician service.