biarmic

Hi everyone,

I bought a 2014 Audi A4 on February. I didn’t realize that the MMI wasn’t working when I bought it. I know it’s my bad. I should’ve checked. MMI was turning on for 10 seconds after ignition and go dark.

After searching on this forum, I opened the trunk box only to see that there’s an antifreeze bottle on top of the amplifier that leaked. I bought an optical loop to bypass it, and MMI started working. But obviously there’s no audio coming from the speaker.

I attached the serial number of the old amp. I bought a 4G0 035 082 G unit from eBay. I plugged it in, but it didn’t work. Nothing actually changed. It has the same behavior as the old amp. I doubt that the new unit is also blown. Can the reason be component protection?

If the reason is component protection, I can try the soldering trick. I remember how to do it from my engineering classes. I can take the 8-pin chip from the old amp and put it in the new amp.

Also, thank you SMac770 with all the information you provided in other threads.

SMac770

That's actually a radio unit with integrated 6-ch amp. The standalone J525 amp unit has fins, and is only present with a B&O sound system when the vehicle has MMI 3G.

You'd want to scan for DTCs and see if the component protection one is active (it will be, there's no way for it not to be when you replace the radio or amp units like that). But audio for something like handsfree phone call should still work. Normally, CP would mute or mess with entertainment audio sources. Navigation audio should also work. So you might check those audio sources.

But you'll also need to check the coding of the unit. It would well be the unit is coded for an external amp, if it was used in a B&O vehicle before. I don't know the long coding helper tips for the coding bits of that unit as I don't have MMI 3G myself to open it and look. But I know the subject has come up in some threads before.

biarmic

A mechanic from the dealer I bought the car from ran diagnostics after putting the new radio/amp unit. It was giving no communications/signal for the radio. MMI was shutting itself off after 10 seconds. I thought it could be because of component protection. The only way I can make MMI work is to put the optic loop on again.

The mechanic claimed that the wiring of the car was done wrong and he needs to change that to make it work. I don’t think he knows this car well.

What should be my next step? Should I check the cables going into the unit? Open the old radio/amp unit to see the board?

SMac770

Then the new unit is probably not powered. Component protection will create some annoyance (muting entertainment sources, etc), not complete failure. The MMI going down because the ring is broken is due to a device failing to operate at a fundamental level. Which is why replacing the unit with the bypass plug allows the MMI system to stay operational.

So assuming the new unit is not defective, then the most likely issue is the unit is not getting power. Have you checked the voltage across pins on the quad-block plug that supply 12v and ground? The large red/yellow and the large brown wires. You should measure battery voltage from the red/yellow to the brown. If you measure 12v across those wires, but you do not see one of the optical ports (on the device) emit red light when you connect the quad-block, I'd had to assume the device is not working. If you do not measure 12v, then try between the red/yellow and the battery negative, and between the battery positive and the brown. Ie, is it the red/yellow lacking 12v, or is the brown not a good ground (given the description of how you ended up in this whole situation in the first place). If no 12v, back up the red/yellow wire to the fuse in the right rear for the radio/amp and check it. MY14 have come up with issues of corrosion breaking 12v delivery to the right rear fuse holders before.

biarmic

I checked the red/white and brown wires with a multimeter. It showed 12V. I was confused because what are the odds of having 2 broken radio/amp units?

I put that plug back into unit, didn’t see any red light emitting from the unit. I put the optic cable into the unit. When I turned the MMI on, it didn’t go dark this time. It stayed on and loaded the radio. FM channels were different and texts were changing when I clicked on one of them. They got removed from the list one by one, maybe because I was in a parking garage. But no audio was coming. The “media unit” didn’t load though. How could this happen? Could it be because of a failed synchronization between MMI and radio because some time passed before I plugged the optic cable in?

I will try again tomorrow. I didn’t do hard reset. Maybe it needs to reboot.

SMac770

That the MMI is staying up is an improvement. If the CP is active (it will be, but you should be scanning for DTCs and seeing the CP DTC is present and engaged), then testing audio from entertainment sources is not productive. Test the audio from a non entertainment source. Nav, Bluetooth handsfree, etc. And you still have to check the unit's long coding to make sure it's configured for internal amp and not external amp. But that would come up in the DTCs. One should always own a scan tool if they own an Audi. I recommend https://store.ross-tech.com/shop/vchv2_ent/ but at least something like OBDeleven if you don't have a Windows laptop to run VCDS.

biarmic

Thank you SMac770.

I tried again this morning with a hard reset. It does the same thing. I connected my phone via Bluetooth, tried to play songs, and called someone. No audio from the speakers. So, the most probable reason is that this unit was previously used in a car with a B&O system and is configured for an external amp, right?

Can the mechanic recode it with a scanner? I don't know what brand/version his scanner is. I think I saw something like "OBD8" written on it (It made me think of the D8 die). I don't know if that's "VCDS compatible." How can I find the correct coding? Do I need to change a bit somewhere? The mechanic may not know this well.

After this recoding is done, I will need to remove component protection somehow. How much does it affect the sound? I will only use my phone to play music. But as I said, I can try to swap the CP chips of the old and new units.

SMac770

If it can do long coding. VCDS can do long coding, OBDeleven can do long coding, no idea if his tool can do long coding. It's a specific type of action for VW/Audi control modules, so anyone who works on those vehicles should be familiar with the task. The specific coding appears to be revealed in this thread: https://www.audizine.com/forum/showt...-(Mobridge-DA2)

CP active will make listening to entertainment sources either impossible (mutes all entertainment sources) or annoying (mutes half the car, or mutes intermittently every few seconds). The point of CP is to make use annoying until it's addressed. So called "anti-theft" policy. So having a non-broken unit to get MMI to stay operating is one advancement, but you're not getting entertainment audio back until the CP is reset.

biarmic

After placing an order for OBDeleven, I took both radio units to swap their CP microchips. After some research, I learned that they’re called EEPROM and look like this:



I opened the old radio unit and inspected it to locate this microchip. I also found where it blew up:



I found only one such microchip inside the old radio unit. I used a hot air soldering machine and a tweezer to swap these microchips, hoping that I fixed CP.

I received my OBDeleven today. After long coding the radio unit to use its internal amplifier, audio started working. However, it still shows CP fault in OBDeleven. Radio gets interrupted every second and media audio doesn’t come from left speakers (although it doesn’t get interrupted).

OBDeleven shows two CP faults and a no signal fault for the radio. At the end, I’m happy that it works but I wish I could fix CP without spending hundreds on an Audi dealership. I wonder if there’s another EEPROM microchip inside the radio unit or if I screwed up when I swapped them.

SMac770

It could be the chip was not a CP chip, that the CP is stored elsewhere. Or it could be the chip was already damaged. That's one of the issues with a service I'm looking at for fixing my MMI 2G B&O amp. They're just going to swap out the inside board with a replacement and move the CP chip over. But if the water damage already toasted the CP chip, then I'm stuck back to the original CP chip of the replacement and needing to have CP reset using ODIS.

There are discussions of reading/writing the EEPROMs directly, such as https://www.audienthusiasts.com/Info...nt_EEPROM.html
Confirming the original CP chip can be read would be a start. But that's more tools to put in hand.

VCP (VAG COM Pro) is another scan tool that can do memory reading/writing with the control modules. People use it as well to read the old EEPROM value and write it to the new unit. All of these are about trying to assign the original id to the new unit so nothing has to be done with the CP master, the J533. Which is what ODIS (dealership tool) would just do.

Unfortunately, the hands on with the CP is outside my experience. I do need to get a soldering iron; the pile of stick drift game controllers is getting out of control.