This document specifies data link independent requirements of diagnostic communication services. These allow a diagnostic tester (client) to control diagnostic functions in an in-vehicle electronic control unit (ECU, server) such as an electronic fuel injection, automatic gearbox, anti-lock braking system, etc. connected to a serial data link embedded in a road vehicle.

This document specifies diagnostic communication services, which allow the diagnostic tester (client) to stop or to resume non-diagnostic message transmission, to read vehicle identification data and real-time sensor data, read and clear diagnostic information, control actuators, start/stop routines, and many more functions to assist in diagnosing the vehicle's electronic systems.

This document does not apply to non-diagnostic message transmission on the vehicle's communication data link between two electronic control units. This document does not restrict an in-vehicle on-board tester (client) implementation in an ECU/server in order to utilize the diagnostic communication services on the vehicle's communication data link to perform bidirectional diagnostic data exchange.

This document does not specify any implementation requirements.