The body bus (K-bus) in the E38 is, in the same way as the diagnosis bus (D-bus), the instrumentation bus (I-bus) and the peripheral bus (P-bus), a serial data link between control units.
The connected control units exchange information via the K-bus, e.g. sensor values or lamp status.
The following control units can be connected to the K-bus:
The automatic heating/air conditioning control system (IHKA) can be recognised by separate operation of the air distribution on the driver/passenger side whereas the air distribution in the heating/air conditioning control system (IHKR) is adjusted by a central control wheel. In the heating and air conditioning control system (IHKR), the air distribution is adjusted by means of a central control wheel.
The automatic headlight vertical aim control (LWR) is installed only in conjunction with xenon headlights. In contrast to the manual headlight vertical aim control system, it features no control for vertical adjustment of the headlights.
The external radio remote control for the central locking systems (FBZV) is installed as a separate control unit only up to 9/95. As of 9/95, the radio remote control feature is integrated in the general module.
The functional principle of the K-bus is comparable to that of a telephone conference circuit. All participants are interconnected via the K-bus. Every participant can both receive as well as transmit messages via the K-bus.
The K-bus is designed as a single-wire bus system, i.e. the K-bus is a wire system which is used to transmit and receive messages.
The high data transfer rate on the K-bus (approx. 10,000 bit/sec) enables distribution of messages between the control units virtually without delay.
DIS diagnosis telegrams are sent to the electronic instrument cluster via the diagnosis bus (D-bus). From the electronic instrument cluster (IKE) the diagnosis telegrams are routed to K-bus control units. The response telegrams of the K-bus control units are sent back also via the IKE to the DIS.