No Audio, No MMI function even after Amp repair

[BG_AG]

I am super stuck with this issue have read all the posts and even had this car at 034 to help a bit with the problem. I randomly lost audio and black screen on the mmi a few months ago. I checked all the fuses and connections I could. I ordered the fiber optic loop off amazon to loop out the amp on the car meanwhile I had the car at 034 Motorsports for some maintenance and had them check all the fuses and power to the MMI they said everything checked out good. Installed the fiberoptic loop and I get the MMI back and full function but no audio. After looking on the forum here I am thinking the B&O amp is the culprit. I send the amp out the Paulison for repair.

Finally this weekend get time to put everything back together and with everything installed correctly I still get a black MMI screen. I did a hard re-start a few times and it will come on for maybe a few seconds and then go off. If I put the loop back in I get everything working besides Audio. Ugggggg super frustrating problem that I just want resolved.

Am I missing some fuses to check? Do I need to get someone to clear a code for me to get this back working? Anything else here I am missing?


Car is a 2011 Avant with the B&O system and RSNAV installed on it. The RSNAV was working great for a month or two then this happened

[Smac770]

Ok, so the amp is still not working. Or the amp is not powered.

To confirm, everything connected as from the factory, MMI comes up and then goes down. If you remove the optical cable from the amp and plug the optical cable into the bypass loop instead, MMI comes up and operates fine (minus the lack of audio output from the speakers). Thus concluding the amp is breaking the optical loop. Be it a broken optical connection / processing in the amp, or the amp not powering up due to no power or an internal failure.

And this is still the case after the amp came back?

The J525 amp should be powered by fuse 3 (1 is towards you, 12 is towards the chassis wall) in row E (rear most row) in the fuse block behind the cargo hold right cover. It is term 30, and so should always show 12v. Do you read 12v on both fuse test pads (the little exposed metal slits on the top of the fuse) of that fuse when measured to chassis ground (you'll see a ground post there below the J393)? If true, then go and unplug the 32-pin plug from the amp (MMI+B&O, the amp should have 32-pin, 18-pin, and optical plugs on it). The two big pins are the 12v and ground. Do you measure 12v between those two pins?

If so and you remove the optical plug and then plug in the 32-pin plug, do you see a red light in one of the optical ports?

[BG_AG]

Ok, so the amp is still not working. Or the amp is not powered.

To confirm, everything connected as from the factory, MMI comes up and then goes down. If you remove the optical cable from the amp and plug the optical cable into the bypass loop instead, MMI comes up and operates fine (minus the lack of audio output from the speakers). Thus concluding the amp is breaking the optical loop. Be it a broken optical connection / processing in the amp, or the amp not powering up due to no power or an internal failure.

And this is still the case after the amp came back?

The J525 amp should be powered by fuse 3 (1 is towards you, 12 is towards the chassis wall) in row E (rear most row) in the fuse block behind the cargo hold right cover. It is term 30, and so should always show 12v. Do you read 12v on both fuse test pads (the little exposed metal slits on the top of the fuse) of that fuse when measured to chassis ground (you'll see a ground post there below the J393)? If true, then go and unplug the 32-pin plug from the amp (MMI+B&O, the amp should have 32-pin, 18-pin, and optical plugs on it). The two big pins are the 12v and ground. Do you measure 12v between those two pins?

If so and you remove the optical plug and then plug in the 32-pin plug, do you see a red light in one of the optical ports?

The amp still seems to be taking down the MMI.

With everything plugged in as it should be I get a black MMI and no audio.
-I also get no lights on in the console controls when functions are pressed.
-I can hard re-start the MMI and it blinks on full function for a few seconds but then goes off

With the Optical Loop Plugged in bypassing the Amp I get full MMI Function but no Audio
-I get lights on in center console controls when functions are pressed

With Car on I am getting a red light in the optical port to the amp and 12+ volts at the rear 30amp Fuse with the loop bypass and without. This and the MMI popping on after the hard restart leads me to believe I am getting power to everything. Correct?

I am waiting to hear back from Paulison to hear if he properly bench tested the Unit before sending it back.

[Smac770]

You didn't go the extra step as I said. So there's 12v at the fuse. But the amp needs it at the plug. Did you take the 32-pin plug off and check for 12v across the two large pins on the plug? Maybe there's a break in the wire from the fuse to the amp.

You have red light on one port on the optical cable that goes into the amp, as expected. But do you have a red light on one port in the optical socket in the amp when the amp is powered (after you confirm 12v at the 32-pin plug)? The amp has to receive the red light from the upstream device, and then it generates red light to the downstream device. This is why you have to have the bypass loop on the cable when the amp is not working, the red light from the radio then carries on to the J533 without a problem and the loop is complete.

To check it using the cable at the downstream device, you'd need to remove the glove box so you can get to the optical plug at the J533. 10 screws, not particularly hard. But I imagine the amp should show a red light in the socket right after power connection.

[BG_AG]

Ok Smac770 you are right I skipped a step. I was rushing to get back into the house to help with our new baby :)

Ran outside tonight and it seems I am not getting voltage at those two large pins on the 32-Pin Plug :/ I will check again tomorrow when it is light out again. I also ran through the volume settings in the MMI when I had the car on after plugging everything back together and I found all the text/ settings greyed out and unable to select in addition the treble, bass, fader... were all dialed down to the lowest setting and I can not change them with the dial in the center console.

A break in the wire from the amp to the fuse? Any idea where this wire goes or how to trace it back? Can I jump it?

[DrGER]

Builds after Nov 2011 power J525 from fuse panel F (ST3/SF4). In either case, I'd look for (1) 12V at T32h/1 and chassis ground and (2) continuity between T32h/2 and chassis ground. If either fails, follow that part of the harness, perhaps across the rear cargo floor, to fuse panel F. --g

[Smac770]

"from Nov 2011" in the US 8K wiring diagrams document = B8.5. Global B8.5 entered production in Nov 2011.

[BG_AG]

Builds after Nov 2011 power J525 from fuse panel F (ST3/SF4). In either case, I'd look for (1) 12V at T32h/1 and chassis ground and (2) continuity between T32h/2 and chassis ground. If either fails, follow that part of the harness, perhaps across the rear cargo floor, to fuse panel F. --g

Hmmmmm this may be above my limit of resources and time at the moment. I may have to bring the car in and get some help. Is this a common problem on these cars? I've heard all about the water damage taking out the amp but not wiring issues to the amp.

Paulison wrote me back today saying the amp was bench tested and tested on his Q7

[DrGER]

Hmmmmm this may be above my limit of resources and time at the moment. I may have to bring the car in and get some help. Is this a common problem on these cars? I've heard all about the water damage taking out the amp but not wiring issues to the amp.

A volt-ohmmeter will confirm (1) and (2) from my post #6. Thinking more about this now (and looking at some photos of the empty spare tire well where the starter battery sits), I'd say it's not likely the J525 harness crosses the floor area -- maybe under the rear lock carrier trim panel ? In any case, you should find the red/white power wire from T32h/1 should go to fuse panel F (fuse ST5/3 30A) directly, as SMac notes in post #2. --g

[Smac770]

If you've validated that the fuse has 12v but that you cannot measure 12v at the plug (this would be between the large blades pins 1 and 2), it could be either the power wire from the fuse to the amp, or the ground line from amp to chassis.

Pull the spare to get a closer source of 12v (the battery positive terminal) and measure the voltage from the battery positive post to the ground pin in the plug (pin 2, the brown wire). If it reads 12v, then the ground path from the amp to the chassis appears to be fine.

Now measure the the voltage from the battery negative post to the power pin in the plug (pin 1, white/red). Based on the discussion so far, we expect this to not read 12v, though it should if all was working. This lack of 12v would be your problem.

But you say you read 12v when checking the fuse? This would be the lone green 30 amp fuse in the right most row as seen at this point in this video: https://youtu.be/QkwmpLCiX2Q?t=85
Based on the fuses present, that image is of a MY10 avant.

You can test the fuse by just touching the test contacts exposed on the top of it, checking voltage to the ground post you should find to the left (forward) of that fuse block. There's a test contact on both sides of the fuse; check both.

So if we're at this point where the fuse has 12v but the plug does not, and we know the fuse is in the correct position. Then there's an issue with the white/red wire, at the fuse, at the plug, or in between. The fuse is not blowing, so the wire is not shorted to the chassis. Meaning it's probably just broken along the way. This would seem to be very unusual. Anyway, confirm or refute the assessment thus far. And make sure the fuse is in the right slot, slot 3.