KeyWordProtocol / KWP2000

The KeyWordProtocol 2000 is a standard for the vehicle diagnostics that is defined in the ISO/DIS 14230 standard. It includes the physical layer (cabling / sender / receiver), the data link layer (establishing the data transmission) and the application layer (tester / vehicle applications). The KWP2000 defines a serial data connection, the K-Line, as the topology for all vehicle diagnostic systems.
The K-Line is a bi-directional, 1-wire line to which all controllers are connected. The predecessor of the K-Line was the cabling according to ISO 9141. This also contained an L-Line. Both lines are operated unidirectionally.
In order for the various controllers to be addressed on the K-Line, each controller is given a unique address - the KWP address.

The communication is structured according to the question/answer principle. The test device sends a request defined by the protocol to the controller and the controller replies to this request. This reply can contain requested data or just the information that the request has been received successfully.
As the communication only ever takes place between a controller and the diagnostics tester, the communication speed - baud rate - can be negotiated between the two participants. Transmission rates of 9,600 to 57,600 baud are typically used.

The UDS protocol is the successor to the KWP2000 protocol.