Audio System/Instruments - Various System Complaints

SI B61 15 02
General Electrical Systems

November 2011
Technical Service

This Service Information bulletin supersedes SI B61 15 02 dated February 2006.

[NEW] designates changes to this revision

SUBJECT
MOST Bus Diagnosis

MODEL
All models equipped with a MOST Bus

SITUATION
The customer may complain of one or more of the following:

^ Crackling or popping sounds from all speakers

^ Loss of audio

^ The control display is constantly displaying the "BMW" banner

^ The iDrive controller is not responsive

^ The control display is blank, white or frozen on the current menu screen.

CAUSE

Possible causes include:

^ Control module power or ground failure

^ Fiber optic cable connection fault or improper radius

^ Faulty control module

^ Dirty, scratched or defective navigation map disc.

^ [NEW] Control module over temperature.

[NEW] PROCEDURE

1. Diagnose all MOST (Media Oriented Systems Transport) Bus system-related faults stored, using ISTA (Integrated Service Technical Application).

2. If no faults are stored, the "MOST System Analysis" test plan can be called up via the following path in ISTA; "Function structure / 03 Body / Audio, Video, Telephone, Navigation (MOST combination) / MOST functions".

3. Control module over temperature faults can be diagnosed with test plan "MOST device; excess temperature switch off" found via the following path in ISTA: "Function structure / 03 Body / Audio, Video, Telephone, Navigation (MOST combination) / MOST functions".

If a control module becomes too hot, the control module switches off for up to 10 minutes to protect internal components from damage. Furthermore, the entire MOST Bus can switch off for 10 minutes. After the control module has cooled down, it regains function again. If the fault "Cutoff excess temperature" is stored in the control module, the control module concerned and the head unit will store the fault. These faults are taken into consideration by the test plan in ISTA.