# KeyWordProtocol / KWP2000 The KeyWordProtocol 2000 is the current standard for vehicle diagnosis 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 a topology for all vehicle diagnostic systems, that was initially intended only for the diagnosis of control units. Some services of the KWP2000 are nowadays also used for loading new software to control units (reprogramming). Communication between the workshop test device (ALADIN) and the individual control units, which are usually made by several manufacturers, has been standardized with the KWP2000. Communication is structured according to the question-answer principle. The test device sends a request defined by the protocol to the control unit and the control unit replies to this request. This reply may contain requested data or just the information whether the request has been received successfully. This is a way of sending a new program version to control units that are reprogrammable (flashable) such as the Voith transmission control unit. For this purpose, the control unit must be equipped with a separate program called Flash Loader. This program receives the KWP2000 messages for reprogramming the other programs from the diagnostic device and executes the commands received, for example, deletes or writes on the flash memory. The data transmission protocol uses key bytes, from which the name 'KWP' has been derived. Up > Higher-level section © by Voith Turbo GmbH & Co. KG send remarks to joachim.ehleiter@voith.com (electronic department) or r.theilacker@voith.com (electronic department)