Data link interfaces have become a requirement for the heavy duty vehicle industry because of the need to share information between individual subsystems. Therefore, it is important for the industry to be familiar with the existing heavy duty vehicle serial data communications standards. SAE has addressed the need to share information between individual subsystems and this paper presents the serial data communications adopted in SAE Recommended Practices J1708, J1587 and J1922 as well as J1939 which is currently under development by the Truck and Bus Control and Communications Network Subcommittee. For a vehicle of the early to mid-1990s, the J1708, J1587 and J1922 documents provide the standards to accommodate general information sharing, detailed diagnostic definition and early powertrain controls integration. The J1939 document being developed will define a network that encompasses all the requirements satisfied by J1708, J1587 and J1922 and any new requirements that arise. This paper, therefore, presents an overview of each standard, the differences between the standards and application information for use of one standard over the other.