Unified Diagnostic Services (UDS) is a diagnostic communication protocol in the electronic control unit (ECU) environment within the automotive electronics, which is specified in the ISO 14229-1. It is derived from ISO 14230-3 (KWP2000) and ISO 15765-3 (Diagnostic Communication over Controller Area Network (DoCAN)). Unified in this context means that it is an international and not a company-specific standard. By now this communication protocol is used in almost all new ECU software projects of vehicle manufacturers such as electronic fuel injection (EFI), automatic gear box, anti-lock braking system, Configurable Engine Mobilizer, Key Controls, Wiper Controls etc.
The diagnostics services able to contact all control units installed in a vehicle, which is using UDS. In contrary to the CAN protocol, which only the first and second layer of the OSI model, the UDS service itself uses the fifth and seventh layers of the OSI model. Modern vehicles have a diagnostic interface for off-board diagnostics, which makes it possible to connect a computer (client), which is referred to as tester, to the bus system of the vehicle. Thus, the messages defined in UDS can be sent to the controllers which must provide the predetermined UDS services. This makes it possible to interrogate the fault memory of the individual control units or to update them with a new firmware.
Services
SID (Service Identifier)