The Lifecycle of a Diagnostic Trouble Code (DTC)
The error codes (Diagnostic Trouble Code - DTCs) used today are based on the flashing codes of control units that were measured by counting. With the increasing complexity of electronics and thus more and more complicated error conditions, such proprietary diagnostic proce-dures are no longer sufficient. Thus, the development led to the currently known 2-byte (OBD legislated codes) and 3-byte DTCs (UDS standardized).
The exchange formats for DTCs
With the data obtained during diagnosis, the cause of the fault and its effect on ve-hicle functions can be analyzed. This is done in order to enable efficient and effec-tive troubleshooting and to be able to continue to operate or repair the vehicle, pos-sibly with restrictions.
Due to the existing cost pressure, it makes sense for vehicle manufacturers and their suppliers to cooperate and use common exchange formats. In embedded elec-tronics development, this resulted in the DEXT format of AUTOSAR and, for off-board diagnostics, the comparable ODX format of ASAM.
The DTC in the control unit
The path of a DTC from detection in an electronic control unit to diagnosis in the workshop is shown in the cover picture (Figure 1).
Application software with diagnostic functions (monitor)
The application software cyclically monitors the signals for compliance with the relevant limit values using monitors also known as diagnostic functions. Compliance or non-compliance with the limit values is signaled to the Diagnostic Manager (DM) in the form of events.