This paper describes the concept of the Diagnostic System Management DSM which introduces an improved object-oriented software architecture in order to meet the high performance and reliability requirements of automotive On-Board Diagnostic Systems (OBD).DSM handles standard tasks and offers services to integrate diagnostic and control functions. This architecture enables the flexible composition of system-independent, reusable function implementations. Hence a distributed software development and software sharing are supported.The module DSM consists of a Fault Code Memory, an Inhibit Handler, a Validator and a Function Scheduler. Special care has been taken to achieve robustness against EMI effects. Bosch will use DSM in the future powertrain control systems.