The document discusses various OBD2 communication protocols used by vehicles, including five main protocols such as SAE J1850 PWM, SAE J1850 VPW, and ISO 9141-2. It clarifies misconceptions about the number of supported protocols by some auto code readers, emphasizing that variants are often mistakenly counted as separate protocols. Additionally, it covers details about non-OBD2 vendor-specific diagnostic protocols and provides examples of OBD2 tools.