The system complexity of automotive E/E systems keeps growing, reaching an impressive number of 100+ million lines of code in recent years. Most of this complexity is due to the algorithm implementation in each Electronic System Unit (ECU) in the vehicle architecture. Additionally, automobiles must meet multiple standards and government regulations (e.g., Diagnostics and OBD), adding contributing factors not just to complexity but also to the development effort, making it very difficult to meet deadlines, milestones, and time to market. This presentation focuses on the AUTOSAR methodology and the architecture solution to diagnostics modeling and workflow using a top-down approach that helps reduce time and effort during ECU development by abstracting the complexity of the implementation and relieving the ECU integrators of exhausting and complex manual work.