What is OBD-II diagnostics and why it's essential before purchase

OBD-II (On-Board Diagnostics II) is a standard port in every car since 1996 that lets us read live data from all electronic systems.

What it reveals: - Active and pending fault codes in the engine - Transmission control unit issues - Airbag and ABS system faults - Live data: temperature, pressure, oxygen - Recent code-clear attempts before sale - Real mileage from the ECU memory

Without this scan you'll miss the hidden faults. Many sellers clear codes before listing, but a pro scanner exposes this via the drive-cycle count since the last reset.