The paper includes the embedded on-board diagnostics system which continuously monitors the system parameters and generates the DTCs (Diagnostics Trouble Codes). The system consists of master-slave communication implemented through CAN network. Sensors are interfaced to slave microcontroller for monitoring various parameters of the system. Master microcontroller produces DTCs to indicate the causes of the fault produced in parameters of system. It is user-friendly system with LCD interface through which user can view parameter values, warning for different parameters of the system.