M25. OBDII (On-Board Diagnostics II)

OBDII (On-Board Diagnostics II) is a standardized system mandatory for all 1996 and newer light-duty vehicles in the U.S. that monitors engine, transmission, and emissions performance, alerting drivers to issues via the "Check Engine" light. It uses a 16-pin connector, typically under the dashboard, allowing scanners to read diagnostic trouble codes (DTCs) and live data.