[cmay119]

Hello all,

I'm trying to return my vehicle to stock form after having an Android Head Unit installed for about 5 years now. Reason for doing this, is I'm going to be likely be selling the vehicle at some point and want to have it returned to stock for that reason.

After removing the Android head unit and reinstalling the RNS850, I now have an issue where it will only power on for a moment to say "Initializing setup" something to that effect and then immediately powers off, mind you after it would do that I could not make the radio turn back on to give the same message. Only after I would leave the Touareg off for a while would it show that message again. Otherwise no response from all button presses and the 5 button reboot.

I came across a thread on this forum where someone was having power cycling issues but was able to get the unit to work for a little bit and then it would power off, he pulled his hard drive out of the MMI 3G and it appeared to at least solve the power cycling issue. Though lost some features like nav and bluetooth from my understanding. So I decided to do the same.

I pulled the harddrive out and low and behold some progress. I can now get to the tuner screen and it will stay on it for about 10 seconds but then alas, power down again. It will respond now to the 5 button reset but only to give me the same result.

At this point, I'm beyond my expertise on really where to go from here. I don't have a VCDS nor do I know anyone who has one. Is there any other troubleshooting tips I can try before finding someone who has that?

When the Android Head Unit was installed an aftermarket backup camera was also used a replica of the OEM one so was install in the originals place but with different wiring than the OEM. Both the RNS850 and the OEM backup camera were reinstalled. I did not do the radio/back up camera install myself, I had Best Buy do it. I know they had to wire the head unit to the speakers directly, bypassing the MOST Fiber Optic system so the volume, microphone controls on the wheel no longer functioned and it didn't communicate otherwise with the Touareg the way the RNS850 does.

The installers that did the work though, seemed to do a thorough job as it otherwise worked well and told me when I want to return it to stock that it's fine to bring back and it's all reversible. Just saying that as there's no indication that they damaged anything as far as the RNS850 is concerned, but I also have don't know that either.

I have a follow up appointment with Best Buy again on Tuesday here to have them reinstall the Android Head Unit and Backup Camera if I'm unable to get this operational again. Unfortunately, the techs who worked on my Touareg 5 years ago seemed much more knowledgeable than the tech who just uninstalled my Android unit as he just cut the speaker wires they had wired up for the Android unit and had no clue on how to reinstall it afterwards after he couldn't get the RNS850 to work. He did not cut the fiber optic wires, that go to the RNS850, they're intact.

He escalated the issue for me to a different location with a "level 2 tech" who will hopefully get me a working radio again. But I would much prefer the stock radio if I had my choice and that's why I'm here asking for assistance. Apologies for being so long winded with this, any help is really appreciated!

 

[DrGER]

@cmay119 -- Your RNS850 is a variant of the MMI3GP system used in Audi models around the same time. The main unit fitted in the glovebox communicates with the radio and external amplifier modules fitted behind rear trim panels via the MOST fiber optic loop. You don't need VCDS (or equivalent VAG diagnostic tool) to debug this, but you might want to get a set of MOST optical loop bypass connectors (one each of female & male) -- the RNS850 main unit will shutdown if the MOST bus is interrupted, say, due to a break in the fiber optic loop when the radio and/or amps is disconnected or unpowered.

The RNS850 sound system is powered either by radio module or a seperate Dynaudio amplifier, both fitted behind the left & right rear trim panels, respectively. So, before continuing, you need to determine the status of the RNS580/sound system components.

BTW, the HDD fitted in the main unit is not requried for the system to operate, but certain functionality will not work (e.g., navigation and media functions) without the HDD. --g

 

[cmay119]

@cmay119 -- Your RNS850 is a variant of the MMI3GP system used in Audi models around the same time. The main unit fitted in the glovebox communicates with the radio and external amplifier modules fitted behind the right rear trim panel via the MOST fiber optic loop. You don't need VCDS (or equivalent VAG diagnostic tool) to debug this, but you might want to get a set of MOST optical loop bypass connectors (one each of female & male) -- the RNS850 main unit will shutdown if the MOST bus is interrupted, say, due to a break in the fiber optic loop when the radio and/or amps is disconnected or unpowered.

The RNS850 sound system is powered either by radio module or a seperate Dynaudio amplifier, both fitted behind the right rear trim panel. So, before continuing, you need to determine the status of the RNS580/sound system components fitted behind the right rear trim panel.

BTW, the HDD fitted in the main unit is not requried for the system to operate, but certain functionality will not work (e.g., navigation and media functions) without the HDD. --g

Thank you so much for responding DrGER, you're one of the most knowledgeable people on this subject, based on other threads with similar issues! So I really appreciate your assistance! I believe I have a fiber loop I purchased at the same time I purchased the Android Head Unit, I'll look for it. Do you know the process for accessing the amp? I'm not seeing any tutorials specifically on youtube or here. Apologies if it is posted somewhere, my searches have been fruitless.

 

[DrGER]

@cmay119 -- Take a look at the Google Drive folder HERE (not my collection). Start with "Communication" PDF. According to this repair manual, the radio module (R) is mounted behind the right rear trim panel, while the sound system amplifier (if fitted), is mounted behind the left rear trim panel. Look at pp 19 - 21 for accessing and removing the Radio module. If you know the Treg has Dynaudio, you will also need to access the amplifier module. --g