Audio System - No Audio/Screeching Sound When Cold
91 08 1122016657/2
November 11, 2008.
Supersedes Technical Service Bulletin Group 91 number 07-58 dated December 10, 2007 for reasons listed below.
Affected Vehicles
91 BOSE 4000 Amplifier - No audio or screeching sound in very cold condition
Condition
The customer may experience the following condition after entering his vehicle in very cold weather conditions (< -12C, 5F):
- No audio in all sources as long as vehicle is cold. After disconnecting the amplifier or a few minutes of driving (warming up), the audio returns and functions normally. The MMI menu is displayed and working properly all the time.
- Screeching sound, after opening the vehicle door (MMI system awakes). After disconnecting the amplifier or a few minutes of driving (warming up), the audio returns and functions normally. The MMI menu is displayed and working properly all the time.
- Sporadically, DTC 01044 may be incorrectly stored in 47 - Sound system.
Technical Background
A slow internal voltage supply initialization (due to ambient temperature) is the root cause of an instable working processor. Software update of the amplifier will correct this issue.
Production Solution
Introduction of the BOSE 6000 Amplifier.
Service
Since the vehicle is usually warmed up when it arrives at the dealership, the symptoms may not be present. If the customer is complaining about this condition and the temperature was low at that time, a Software Zug update has to be performed.
Procedure:
1. Determine the correct Update CD as shown above.
2. Connect an approved battery charger or maintainer to the designated charging studs to ensure a stable voltage supply during the software update.
3. Eject inserted customer CDs from the CD changer, and load the Update CD in the first slot.
4. Press and hold the Setup button and then the Return button until the red menu appears.
5. Press the lower right soft key of the MMI Control Head to enter the SWUpdate menu.
6. Use the central control knob of the MMI Control Head to select CD-ROM and then Standard.
7. Scroll down the component list with the central control knob and select Start download.
8. Obey the warning on the next screen, scroll down and select OK to run the update.
9. After completion of the software update, restart the MMI.
10. Verify the new software part number in the amplifier (Adr. Word 47), erase all sporadic fault codes and perform the SVM Update with the SVM codes above.
Warranty
Required Parts and Tools
Additional Information
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service manuals for the latest information.