An OBD-II scanner is a diagnostic tool used to communicate with a vehicle's onboard computer system. It connects to the OBD-II port, typically located under the dashboard, to read and interpret error codes generated by the vehicle. These codes help identify issues related to the engine, transmission, and other critical systems, allowing for efficient troubleshooting. Using an OBD-II scanner can help car owners and mechanics monitor vehicle performance and emissions. It provides real-time data, such as engine temperature and fuel efficiency, and can assist in ensuring that the vehicle complies with emission standards. This tool is essential for maintaining vehicle health and safety.