Abstract: A vehicle diagnostic system and method utilizing a plurality of diagnostic data corpuses. A first corpus comprises conventional and well-known diagnostic data useful in a broad range of common service tasks. A second corpus comprises less well-known diagnostic data useful in less common service tasks. One or more specialty corpuses may comprise obscure, protected, or emerging diagnostic data for the last-common tasks specific to particular manufacturers of the vehicle or its components. The second corpus and one or more specialty corpuses may offer access only to users that have acquired sufficient authorization.