The increasing use of electronics in transport systems, such as the automotive and avionic domain, has lead to dramatic improvements with respect to functionality, safety, and cost. However, with this growth of electronics the likelihood of failures due to faults originating from electronic equipment also increases. Although permanent failure rates are constantly diminishing due to improvements in manufacturing, the downsizing of semi-conductor features has lead to a significant increase in transient system disturbances. Furthermore, transients are frequently the precursors of upcoming permanent failures. In order to cope with this development, a diagnostic subsystem must especially be designed to detect and analyze such transients to reduce the failure-not-found ratio in today's systems. Therefore, diagnostic detection mechanisms must be devised that refrain from traditional error detection techniques operating only on component-local data in favor of a system-wide view to detect and analyze correlated failures and infer the corresponding fault.In this work, we present Out-of-Norm Assertions (ONAs) as a diagnostic mechanism operating on the distributed state to detect correlated component malfunction. ONAs take the characteristics of faults in the time, value and space domain into account in order to discriminate between different types of faults that are affecting the operation of the distributed system. Since ONAs are specified on the interface state mutual error detection of interface state variables is performed. In contrast to bivalent assertions that need to indisputably decide on correct or incorrect system states at the time of occurrence, the proposed ONAs are also useful in the detection of system irregularities that cannot be forced into the predominant bivalent assessment scheme.