What is UDS (Unified Diagnostic Services) and how is it used?

UDS (ISO 14229) is the standard diagnostic protocol for automotive ECU communication. It defines: Service IDs for functions like reading/clearing DTCs, data reading/writing, routine control, and ECU programming; Request-response message structure; and Session modes (default, programming, extended diagnostic). UDS runs over CAN (ISO 15765), LIN, FlexRay, or Ethernet transport layers. Applications include factory diagnostics, service tool communication, end-of-line programming, and field software updates. UDS replaced older protocols like KWP2000 as the industry standard.