On-board diagnostics II (OBD-II) is a new automotive device, which can provide the vehicle's self-diagnostic and reporting capability to the vehicle owner or repair technician. And the vehicle owner or repair technician can understand the status of the various vehicle subsystems. These vehicle's self-diagnostic reports are very basic material for the car big data. Currently marketed OBD-II system can only be used for small cars. However, the large vehicle is the main cause of car accident. Therefore, the proposed OBD-II device is suitable for the niche market of the bus and commercial vehicles.