OBD-II scanner

OBD-II, short for On-Board Diagnostics generation two, is the standardized diagnostic port required on cars sold in the United States since the mid-1990s. An OBD-II scanner plugs into that port, usually located under the dashboard, and communicates with the car's computer to pull trouble codes, the same codes a mechanic reads to figure out why a check-engine light came on.

Basic scanners simply read and clear codes and display a short description, which is often enough to identify a common issue like a loose gas cap or a failing sensor before deciding whether a repair needs a professional. More advanced scanners add live sensor data, freeze-frame information from the moment a fault occurred, and sometimes manufacturer-specific codes beyond the generic set.

A scanner will not diagnose everything, and a code is a starting point rather than a final answer, since the same code can point to more than one underlying cause. Bluetooth models that pair with a phone app are convenient for quick checks, while a standalone handheld unit tends to be more reliable in areas with poor phone connectivity or when working on an older vehicle.