Keyword Protocol 2000, abbreviated KWP2000, is a communications protocol used for on-board vehicle diagnostics systems (OBD). This protocol covers the application layer in the OSI model of computer networking. The protocol is standardized by International Organization for Standardization as ISO 14230.
One underlying physical layer used for KWP2000 is identical to ISO 9141, with bidirectional serial communication on a single line called the K-line. In addition, there is an optional L-line for wakeup. The data rate is between 1.2 and 10.4 kilobaud, and a message may contain up to 255 bytes in the data field.
KWP2000 is also compatible on ISO 11898 (Controller Area Network) supporting higher data rates of up to 1Mbps. CAN is becoming an increasingly popular alternative to K-line because the CAN bus is usually present in modern day vehicles and thus removing the need to install an additional physical cable.