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E38 K-Bus System Overview

The K-bus is a serial data link between control units in a vehicle that allows connected units like the climate control, instrument cluster electronics, headlight aim control, and remote keyless entry system to exchange information. It functions similarly to a telephone conference circuit, connecting all participants to transmit and receive messages through a single wire bus system. The high data transfer rate of around 10,000 bits per second enables virtually delay-free distribution of messages between control units. Diagnosis telegrams are sent through the K-bus from the instrument cluster to other control units and response telegrams are returned the same way during diagnostic testing.

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157 views2 pages

E38 K-Bus System Overview

The K-bus is a serial data link between control units in a vehicle that allows connected units like the climate control, instrument cluster electronics, headlight aim control, and remote keyless entry system to exchange information. It functions similarly to a telephone conference circuit, connecting all participants to transmit and receive messages through a single wire bus system. The high data transfer rate of around 10,000 bits per second enables virtually delay-free distribution of messages between control units. Diagnosis telegrams are sent through the K-bus from the instrument cluster to other control units and response telegrams are returned the same way during diagnostic testing.

Uploaded by

Michal Piratz
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K-BUS

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.

Design and function of the K-bus

The following control units can be connected to the K-bus:

- FBZV: External radio remote control for central locking system


- GM 3: General module of ZKE3
- IHKA/IHKR: Automatic climate control
- IKE: Instrument cluster electronics
- LWR: headlight vertical aim control
- FGB: Rear compartment blower
- AIC: Automatic interval control
- EWS: Electronic vehicle immobilization, as of 09/96 on K-bus.
Identification features of K-bus control units

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.

Function of the K-bus

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.
Diagnosis with K-bus control units

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.

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