Automative

Diagnostics feature is actually to check the state of functions, subsystems, sensors and actuators for errors and saving them in a memory which is typically known as error memory.


The errors are referred with the help of a predefined hex-code named as “Diagnostic-Trouble-Code or DTC” inside the electronic-control-unit.


Detection and saving of the DTC’s, their states along with their environment-data in error- memory is performed most of the time parallel to normal system-functions and is also referred as “onboard diagnostics or OBD” typically because this is happening inside the board or inside the electronic control unit (ECU).


The stored errors can be read by an external tool making use of a predefined protocol (e.g. Unified Diagnostic Services) over Controller-area-network also known as CAN. Since in this process a device outside the electronic control unit i.e. the Tool is involved, it is typically known as “offboard diagnostics“.


These OBD codes were standardized using SAE J2012 and ISO 15031-6 standards which, to our knowledge, contain about 11 000 definitions in the most recent version.


OBD-II is an improvement over OBD-I in both capability and standardization. The OBD-II standard specifies the type of diagnostic connector and its pinout.


OBD-II Diagnostic Trouble Codes are 4-digit, preceded by a letter; P for engine and transmission, B for Body, C for Chassis and U for Network.