A car scanner is a diagnostic tool used to read and clear error codes from a vehicle’s onboard computer. It connects to the car via the OBD-II port, typically located under the dashboard. Scanners help identify issues in systems like the engine, transmission, ABS, and airbags. Advanced models display live data, perform system tests, and support ECU programming. Mechanics and DIY users rely on scanners for quick and accurate troubleshooting. Using a scanner can save time and money by pinpointing problems before costly repairs.