MMI Optical Bus Errors after Battery Replacement – No Sound / Audio Looping

[stom1]

Hi everyone,

After replacing the battery on my 2007 Audi Q7 TDI, the car was without power for about two hours.
Once I installed the new battery, I ran an Optical Bus Diagnostic and got the following results:

Thursday, 13, November, 2025, 18:42:35:12345

VCDS Version: Release 24.10.0 (x64)

Data version: 20251001 DS350.0

www.Ross-Tech.com



VIN: WAUZZZ4L67DXXXXXX License Plate: -

Mileage: 241,000 km Repair Order: -



--------------------------------------------------------------------------------

Control Module Part Number: 4L0 910 468

Component and/or Version: J533__Gateway H06 0040

Optical Bus Diagnostic: Standard



Controller Electrical Optical



19-CAN Gateway OK ERROR

07-Control Head (High/D3) OK ERROR

0E-Media Player 1 OK OK

47-Sound System OK ERROR

56-Radio OK ERROR

37-Navigation

--------------------------------------------------------------------------------

The MMI system itself is working, but the radio plays sound for about 3 seconds, then cuts out for about 1 second — and this loop repeats endlessly.
The CD changer accepts and ejects discs just fine, but there’s no audio output.

Has anyone experienced this issue before?
Any ideas on what might be causing the optical bus errors or the repeating sound dropouts?

I suspect it might be related to a MOST ring break or possibly a power supply issue with the amplifier.

Thanks in advance for your help!

Scan performed with VCDS.

 

[Boki Ar]

We need full Auto Scan to be able to help.

 

[Dr Sheldon]

e,

After replacing the battery on my 2007 Audi Q7 TDI, the car was without power for about two hours.

Post a copy of the invoice for the battery

 

[Dr Sheldon]

Has anyone experienced this issue before?

Yes

 

[stom1]

Yes

 

[stom1]

Post a copy of the invoice for the battery

VARTA DYNAMIC AGM​

Range: 90-110Ah
Polarity: R+
Vehicle type: CARS
Dimensions: 393x175x190
Warranty - months: 36.0
Pole type: 1
Mounting: B13
Voltage: 12.0
Height: 175
Depth: 190
Capacity: 110Ah
Starting current: 920A

 

[stefdds]

Scan performed with VCDS.

As noted in post #2 (Boki Ar) .

Sticky - How to post an Auto-Scan

Using the classic, Windows-based VCDS: Also, please wrap your Auto-Scan data in CODE tags, like this: Chassis Type: 4G0 Scan: 01 02 03 05 08 09 0E 10 13 15 16 17 19 28 36 3B 3C 42 44 46 47 52 53 55 56 5F 62 72 82 84 85 8B 8E 8F 90 VIN: WAUBGAFC5CN015352 01-Engine -- Status: OK...

forums.ross-tech.com

 

[Dr Sheldon]

Has anyone experienced this issue before?
Any ideas on what might be causing the optical bus errors or the repeating sound dropouts?

YES !

 

[Uwe]

YES !

How is this helpful?

-Uwe-

 

[stom1]

As noted in post #2 (Boki Ar) .

Sticky - How to post an Auto-Scan

Using the classic, Windows-based VCDS: Also, please wrap your Auto-Scan data in CODE tags, like this: Chassis Type: 4G0 Scan: 01 02 03 05 08 09 0E 10 13 15 16 17 19 28 36 3B 3C 42 44 46 47 52 53 55 56 5F 62 72 82 84 85 8B 8E 8F 90 VIN: WAUBGAFC5CN015352 01-Engine -- Status: OK...

forums.ross-tech.com

Has anyone experienced this issue before?
Any ideas on what might be causing the optical bus errors or the repeating sound dropouts?

We need full Auto Scan to be able to help.

[REMOVED] only scans from legitimate Ross-Tech interfaces are permitted.

 

[Mike R]

If you decide to buy a real Ross-Tech product through Ross-Tech or one of our officially recognized distributors we will be happy to help you. Let us know if you do so that we can update your status here on the forum.

-Mike