instrument cluster BMW 7 SERIES LONG 2003 E66 MOST Bus Diagnosis Workshop Manual

9
MOST Bus Diagnosis
Audio Master
As audio master, the ASK has the task to collect and process all the audio signals of the
vehicle and to distribute them to their destinations.
The ASK controls all the acoustic requests from the Control Display. The changes in the
level of a signal is not sudden, but smooth, e.g. during suppression, insertion and fading
out or temporary suppression of the signal at the destination: Because of this, a high-qual-
ity acoustic sound is obtained.
The ASK also assumes the generation and preparation of different acoustic signals, e.g.
PDC signals and warnings. In the event of a request for a warning or caution signal from
a control unit, the ASK provides a clean acoustic change of the signals.
 Audio data
All audio data from any control unit are converted by the ASK into digital audio AF
format at a sampling rate of 44.1 MHz.
 Categorization of audio sources
All possible audio sources are divided into different groups according to priority. Warning
signals have priority over any other audio source. Mixing of lower priority audio signals
(e.g. navigation, radio) is possible.
 Generation of acoustic gongs
These are acoustic alarm signals which help the driver perceive sounds according to a
system. The different sounds, requested by the different control units, (e.g. gongs, PDC,
etc.), must be generated only in association with a visual indication. These come from
the instrument cluster and the Control Display.
The following sounds can be generated in the ASK.
 Beeping for the PDC.
 Various Check Control and warning gongs.
Note:
A maximum of three sounds can be produced at once. Sounds are produced in order of
importance. Sounds requested exceeding three will be lost.
Connection Master
As connection master, the ASK must provide channels to the equipment connected to the
bus and distribute the audio signals on the outputs (loudspeakers).
The connection master also controls the basic Hi-Fi or the LOGIC 7 Hi-Fi amplifiers.

10
MOST Bus Diagnosis
CD Changer Audio (CDC)
The CD changer is a slave control unit in the MOST framework.
Navigation System (NAV 01)
The control unit of the navigation system has controller tasks and slave functions in the
MOST framework.
Slave Control Units
The following control units are slave control units:
 Kombi (control unit of the instrument cluster)
AVT
 LOGIC7
 SVS Speech processing system
 Telephone
 MMC
Component Locations
Located in the dashboard assembly:
 Control Display
 CD Changer
 ASK
 Kombi
 OPPS Connector
Located in the luggage compartment, rear left:
 Logic 7
 SVS
NAV
 MMC
 Telephone
Located in the C pillar left side:
AVT

11
MOST Bus Diagnosis
Communication Direction in MOST structure
Important!!! The component sequence of the MOST controllers in the ETM is incor-
rect when it comes to signal transmission direction. The correct sequence is indi-
cated above!
The signal transmission direction of the MOST in a vehicle
with full equipment takes place starting at the Control
Display and travels serially towards the CD changer,
Antenna tuner, Hi-fi amplifier, Speech Processing Module,
Navigation, Multi-media Changer, telephone, Audio
System Controller, Instrument Cluster and again back to
the Control Display.
Counts as 2Counts as 2

12
MOST Bus Diagnosis
Diagnosis
It is important to remember that on the MOST network, messages can only be transmitted
provided the bus ring is complete and fully functional. If there is a ring fault in the MOST
network, the diagnostic system only communicates with the instrument cluster and the
Control Display because both of these modules are directly connected to the K-CAN
System Bus.
The fiber optic signals on the MOST network always travel in one direction and only in one
direction. Signals always originate at the Control Display and travel to the CD changer, AVT,
Logic 7 (if equipped), SVS, NAV, MultiMediaChanger (if equipped), Telephone, ASK, Kombi
and back to the Control Display.
The MOST bus allows intersystem fault memory entries in the individual control modules.
A feature of the system faults is that faults may be entered in a control module although the
control module is OK. Conclusions may be drawn about the cause of the fault, using the
fault information stored in all the control modules.
The possible system faults are:
 Optical wave guide communication fault (All MOST Control Module) FC 111
 A Control Module does not switch a light off (All MOST Control Modules)
 Network wake-up unsuccessful (Control Display (Gateway), ASK, Telephone Only)
FC E18D
 Ring fault diagnosis run (Control Display (Gateway) and Kombi Only) FC E190
The Control Display functions are split between acting as a Gateway and Displaying infor-
mation. The Gateway function serves as the interface between the MOST and the K-CAN
System buses. Although the Control Display is one control module, two control module
names are displayed in the DIS Plus:
 CD Control Display (Gateway)
 CD Control Display
The faults stored in the Control Display are distributed between the Control Display
Gateway and Control Display according to the function of the fault.