The major reason why diagnostics have become an important factor in the trucking industry is the increased complexity of electronically controlled engines. Secondary reasons which influence the growing importance of diagnostic equipment are the increased computational capability of on-board controllers, the addition of the J1708 standard truck communication link, the decreased cost of electronic components, and the increased reliability of electronics. With the release of standardized diagnostics, J1587 RP Rev. 1989, “Electronic Data Interchange Between Microcomputer Systems in Heavy-Duty Vehicle Applications,” the evolution from mechanical systems to electronic systems is paved. This paper describes one philosophy behind the standard, describes the standard, and discusses future service tools for the Industry.