MMI no sound

[tmroth209]

Hello. New to forum, and new to me 2013 a4. I have the basic radio (no nav). Out of the blue, no sound from speakers, no bluetooth, etc. All MMI functions work, just no sound. I checked all fuses - all are good. I have access to spare parts and I swapped in a factory amp (matching s/n) and no change. I realize there is coding issues with a replacement amp, but I thought I may at least hear static if it was a fried amp issue. Trying to avoid a trip to the dealer here. Any other troubleshooting I can do? Any other ideas/prognosis?

Thanks in advance.

[tmroth209]

Got these codes:

00463 - control module for digital sound package (J525):* 004 (no signal/communication - intermittent)
03157 - functionality limited due to communications disruption
00417 left front DSP mid-bass speaker:* 011 - open circuit/intermittent.* This is an old code dating to 2020, so I don't believe its related tot the current problem.**

There is also a component protection code, but I was expecting that since I swapped in a new factory amp.**

Any further insight?* Wondering if the head unit itself is malfunctioning.**

[misterpepper]

I'm no help code-wise but I've had the MMI on my '09 stop outputting sound two different ways. Once the satellite radio receiver went bad and another time it was the component in the glove box that the AMI cable plugs into. Both times my solution was to get a fiber optic "jumper" cable to bypass the malfunctioning component. I'd suggest getting one. They're only $10 or so. Try bypassing different components until you figure out which one is causing the issue and then decide if you can live with it or if you want to just leave it bypassed. Both of mine remain bypassed.

[tmroth209]

I'm no help code-wise but I've had the MMI on my '09 stop outputting sound two different ways. Once the satellite radio receiver went bad and another time it was the component in the glove box that the AMI cable plugs into. Both times my solution was to get a fiber optic "jumper" cable to bypass the malfunctioning component. I'd suggest getting one. They're only $10 or so. Try bypassing different components until you figure out which one is causing the issue and then decide if you can live with it or if you want to just leave it bypassed. Both of mine remain bypassed.

Thanks for the tip. However, my year/basic sound doesn't have a fiber optic connection on the media interface.

Further testing seems to show power in/out amp. Seems like may be a head unit issue.

[RPMtech147]

On the newer stuff with component protection, the sound still works but it does weird stuff, like play on 1/2 the speakers and lowers and raises the volume.

[B8bully]

I'm no help code-wise but I've had the MMI on my '09 stop outputting sound two different ways. Once the satellite radio receiver went bad and another time it was the component in the glove box that the AMI cable plugs into. Both times my solution was to get a fiber optic "jumper" cable to bypass the malfunctioning component. I'd suggest getting one. They're only $10 or so. Try bypassing different components until you figure out which one is causing the issue and then decide if you can live with it or if you want to just leave it bypassed. Both of mine remain bypassed.

Have the link if possible to fiber optic cable? And maybe a link on how to use it?

[RPMtech147]

Have the link if possible to fiber optic cable? And maybe a link on how to use it?

You can get them on Amazon for a few bucks.

[B8bully]

You can get them on Amazon for a few bucks.

thanks i ordered one and tried both AMI and satellite radio receiver im still getting no sound i even tried AMP and still no sound any ideas on what else i can check
? and also doe i have to have all the wires to AMI and receiver unplugged when i connect the loop to it?

[Smac770]

The MOST ring is just that, a ring. A cable goes from device A to device B, the other cable at device B then goes from device B to device C. And around until a cable comes back to device A. The ring is a single loop, it must be continuous. Each cable end plugs into a device. One cable brings the light to the device from the previous device; one cable takes the light from the device to the next device. If any device is not operating, it will not forward the incoming light to the downstream device. The point of the bypass loop is to replace a suspect device with a piece of plastic that simply bridges the two cables together, ensuring the ring is unbroken. If you go breaking the ring elsewhere, such as having other plugs unplugged or multiple devices failed, then the ring is still broken and MMI will not come up.

The better start point is to run the ring break diagnosis application in VCDS. Confirm all devices on the ring respond electrically ok. Any that don't, you need to check fuses and basic operation. After that, the first device in the ring to report not ok for optical, you'd normally look at that or the cabling between it and the previous device. That you have optical on the AMI and a separate sat radio tuner box, I presume you have MMI 2G?

[B8bully]

The MOST ring is just that, a ring. A cable goes from device A to device B, the other cable at device B then goes from device B to device C. And around until a cable comes back to device A. The ring is a single loop, it must be continuous. Each cable end plugs into a device. One cable brings the light to the device from the previous device; one cable takes the light from the device to the next device. If any device is not operating, it will not forward the incoming light to the downstream device. The point of the bypass loop is to replace a suspect device with a piece of plastic that simply bridges the two cables together, ensuring the ring is unbroken. If you go breaking the ring elsewhere, such as having other plugs unplugged or multiple devices failed, then the ring is still broken and MMI will not come up.

The better start point is to run the ring break diagnosis application in VCDS. Confirm all devices on the ring respond electrically ok. Any that don't, you need to check fuses and basic operation. After that, the first device in the ring to report not ok for optical, you'd normally look at that or the cabling between it and the previous device. That you have optical on the AMI and a separate sat radio tuner box, I presume you have MMI 2G?

i dont have a vagcom and yes 2G mmi with B/o system. can i check any of that with OB11? and my radio was working fine until i left my ignition on one day and battery died ever since then it has no sound

[Smac770]

I have no idea if OBDeleven has ring break diagnosis functionality. OBDeleven also cannot read the battery management history log. You'd have to inquire to VoltasIT (who makes OBDeleven) regarding their intentions to improve their product's usefulness for troubleshooting purposes.

Unfortunately, standard scan approach will not be particularly useful since if the ring is down, all the modules on it are inaccessible. So "cannot be reached" for every MOST member is not particularly informative.

The problem is MMI 2G has 9 devices on the MOST ring, whereas MMI 3G has only 3 or 4 (in US configurations). And one of those is hard to get to, the R36 Bluetooth module is in the floor under the passenger seat.

That said, you say "no sound", rather than "MMI down". MMI down implies there's no sound, but the converse is not true. So are you just getting no audio, or is the MMI system whole down? You mention your radio, so is the radio the only source not working?

You had a thread on your issue somewhere, no?

[tmroth209]

Thanks for the thread hijack.

[B8bully]

Yes my MMI works fine I can switch from am/FM, Bluetooth, I can even connect my phone and use GPS I'm just not getting any sound what so ever. And yes I made a thread on the radios forum to see if some one outside of b8 can help. Also my rearview camera doesn't come on when I put it in reverse unless I hit the 3 reset buttons simultaneously while in reverse it's really weird

[Smac770]

If the MMI system is up and functional, it's not an optical ring issue. Either somehow the audio is muted or turned down, or the amp is broken (though not entirely, since it's clearly operating well enough to maintain the ring continuity). Unless the amp is not actually on the ring (the optical cable is plugged into it?). Could be all your speakers are dead? Do you not have any DTCs from the address 47 (sound system, J525)?

I guess it could be the J794 is flaking out; it has to set up all transfers on the optical ring. Have you pulled out the J794 and unplugged and replugged the FAKRA cable that is the backup camera feed line on the back of the J794? Wonder if it's loose. But that too, another "flaky" operating exhibit from the J794. Do a full scan with OBDeleven and post up the history log (no screenshots, please).

[tmroth209]

As to my issue, it ended up being the radio. Very odd considering all functions worked but sound. $50 ebay radio worked, but when powered on car the first time, component protection warning came on display. So, I'll head to the dealer for programming and will be good to go. Thanks all.

[Smac770]

Maybe the pre-amp drivers in the Concert simply died. Not something posted in the past, but as time passes, anything can fail. Did you measure no voltage activity on the low level input lines from the head unit to the amp to point you to a lack of signal from the head unit?