What does the OBDII protocol mean?

[AuroraRose]

OBDII protocol refers to the implementation of standardized detection procedures with strict emission targeting, used for real-time monitoring of vehicle exhaust emissions. The working principle of OBDII is: 1. During normal vehicle operation, the input and output signals of the vehicle's electronic control system vary within a certain range following specific patterns. 2. When the signals from the electronic control system circuit become abnormal and exceed the normal variation range, and this abnormality persists for a certain period, the ECU determines that a fault has occurred in this part. The malfunction indicator light is then activated, and the monitor stores this fault as a code in its internal RAM.