K-Line

The K-Line is a bidirectional bus according to ISO 9141 and ISO 14230-1 in the automotive sector.

Data transmission via the K-Line can only be unidirectional at any one time. Only when a message is finished can it be sent in the other direction.

Example of communication with an engine control unit, 9600 bit/s:

The quiescent level is approx. 12.7V (on-board voltage), for communication the connected diagnostic system pulls the K-Line to ground: