AUTOSAR is the future-oriented reference architecture for ECU software. Clearly specified interfaces, standardized behavior and XML-based data formats are the key features of this standard. In AUTOSAR, diagnostics are handled in the modules DCM (communications) and DEM (fault memory). This article first addresses diagnostics in AUTOSAR and related data formats. Description data in ODX format (Open Diagnostic Data Exchange) represents an alternative to configuring the diagnostic software. The next issue will address the topic of “ODX in the AUTOSAR development process”.