This part of ISO 14229 specifies data link independent requirements of diagnostic services, which allow a diagnostic tester (client) to control diagnostic functions in an on-vehicle Electronic Control Unit (ECU, server) such as an electronic fuel injection, automatic gear box, anti-lock braking system, etc. connected to a serial data link embedded in a road vehicle.It specifies generic services, which allow the diagnostic tester (client) to stop or to resume non-diagnostic message transmission on the data link.