The Service Manual covers all the various systems that are part of a specific chassis, except for detailed specifics on the engines. There are sections, or Groups, for brakes, doors, tune-up specs, axles, transmissions, HVAC, etc.

For detailed engine related information there are other volumes. There is a printed volume for OM615, OM616, and NA OM617 diesel engines, for example. They did it this way because those engines were used in a variety of chassis. Printing these books separately was a more efficient way of providing the information with a minimum of duplication.