Read Data Stream is a fundamental function in automotive diagnostics because it allows real-time visualization of vehicle parameters and sensor data, such as engine RPM, coolant temperature, vehicle speed, throttle position, and many other values generated by the ECU. To access this information, communication is first established between the scan tool and the vehicle’s electronic control module through diagnostic protocols such as OBD-II, UDS, or manufacturer-specific protocols like those used by Toyota. During this process, the scanner sends specific data reading requests using services such as 0x21, 0x22, or 0xA8, and the ECU responds with frames containing the current sensor values. In addition, some vehicles require entering extended diagnostic sessions or performing Security Access procedures to unlock advanced Data Stream functions. For a better understanding and analysis of these communications, we used the CAN Bus Multiplex Trainer tool, which allowed us to observe and analyze the CAN frames exchanged between the scanner and the ECU in real time, making it easier to understand the structure of the messages, the identifiers used, and the correct interpretation of the received data. Understanding the structure of these frames and the way the data is interpreted is essential for performing tests, diagnostics, and proper emulation of automotive modules, allowing real-time monitoring of vehicle behavior and facilitating the detection of electronic faults.
