OBD-II (On-Board Diagnostics, second generation) is the standardised diagnostic system and connector mandated in cars for decades — the 16-pin port and baseline protocols every scan tool starts from.
OBD-II standardises emissions-related diagnostics: the connector, base protocols and generic trouble codes. Everything beyond that — full-system access, special functions, programming — rides on manufacturer-specific protocols layered on top, which is where diagnostic platforms differentiate.
Why it matters
The port being standard misleads buyers into thinking access is standard: modern coverage is a moving software target, and increasingly gated by secure gateways.
Related terms: DTC, CAN FD · Related reading: How Chinese diagnostic brands went global