Automotive diagnostics provide access for manufacturing, service, and forensics of automotive systems, and are present in nearly every vehicle on the road today. These systems provide a large attack surface, and often contain undocumented features. Unfortunately, information about these systems is proprietary, and tools for interacting with them are expensive. In this talk, we’ll introduce automotive networks, then dive into detail about diagnostic systems. Next, we’ll show open source tools for automating the reverse engineering of diagnostic systems, and finish up with some practical examples. Attendees should leave with a better understanding of how their car works, and where to go hunting for vulnerabilities in diagnostics.