The rns-850 has three components.

1. The dash display/interface
2. The players DVD, SD and HD in the glove box
3. The tuner/amplifier in the right rear corner.

All are fused separately.

They communicate via the MOST bus (fiber optic ring).

Locate and test each of the fuses first.

If it is genuinely a display issue pull it out the dash and check the plug. Dirty pins, loose connector etc.

I don't know what diagnostics VCDS would give but it's still worth having if you own a VW.

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This thread may help.

RNS 850 black screen and no 51 fuse blown...

Hi, I recently got the black screen and no 51 fuse blown. The dealer wanted ridiculous money to find and fix the issue 😲. My thoughts are, get the fiber loop thingy, put it on the unit on the rear aft right radio/amp and if culprit, replace with new aftermarket unit (MATCH PP 62DSP). Does...

www.clubtouareg.com

 

Yes, what he said!

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I have no fuses that blew, I checked all fuses on the left and right hand side of the dash, or are there more fuses hidden somewhere else?

Thanks for all the help guys!

 

I believe there is a fuse behind the screen.

 

According to swedishpolarbear the display won't come up if the tuner / amp is bad.

I have asked where he got the fiber looper but no reply yet.

Actually more readily available than I thought... Here I was thinking it was a specialized tool or something.

Amazon.com: YIOVVOM Fiber Most Optic Loop Connector Diagnostic Device Tool Bypass Female And Male Adapter For Benz Audi Mercedes BMW VW Porsche Mercedes Benz, Audi, VW, Porsche Pack of 2 : Automotive

Buy YIOVVOM Fiber Most Optic Loop Connector Diagnostic Device Tool Bypass Female And Male Adapter For Benz Audi Mercedes BMW VW Porsche Mercedes Benz, Audi, VW, Porsche Pack of 2: Electrical - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

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That seems to be a helpful tool to rule out issues. I have ordered the VCDS tool but I will also get this one. I should be able to find the culprit with these tools and help from all you guys!

 

I ran a system check with VCDS and it gave an error on the radio and the display. That is not very helpful... I disconnected the radio and plugged in the fiber loop. Now I get no error on the radio (it says there is no radio which is correct) but still a message on the display. I tried removing the display, I located the top two screws but it is still fixed at the bottom, I can't find any screws. Does anybody know how to remove the display?

Thanks guys!

 

I can't do youtube from work but the google search showed several links.

rns-850 removal - Google Search

 

Unfortunately none of those show how to physically remove the RNS 850 from the dash....

 

Hi all,

Yesterday I started the car and the infotainment system was blank. Nothing works, no radio, media, phone or nav, the screen stays blank. I tried rebooting with the 5 buttons but that doesn't help. I am suspecting the RNS850 unit in the glovebox to be the culprit. Before dishing out $$$ I want to make sure that is indeed the cause of the problem. I don't have VCDS (yet) and I am wondering if it would be able to pinpoint what unit is broken. I tried to find an answer on Ross website but I was not succesful.
My questions:

1. Is VCDS able to tell me what the issue is?
2. Does anybody know a repair shop that could repair the unit? I live in the USA.
3. If I have it repaired, will it need to be recoded by the dealer?

Thanks in advance, any help is much appreciated!
Frank

My 2016 TDi Lux RNS850 radio went blank with message on driver's dash displaying "System is Starting...". VCDS logs

-------------------------------------------------------------------------------
Address 56: Radio
Cannot be reached

-------------------------------------------------------------------------------
Address 5F: Information Electr.
Cannot be reached

Fuse 51 (on fuse panel C) -SC51- 20A - Radio -R- is not blown. I've got the optical M/F loopback connectors on order ($9.49 eBay) and will bypass the tuner when they arrive.

Has anyone determined the root cause of this symptom?

 

Would @Frank914 update this thread? Are you there?

 

Yes, I'm here

VCDS gave me the same message as Texans2's car, Radio can not be found. I bypassed the radio with a fiber loop but that didn't really tell me much. I brought it to stealer who did a diagnostics, turns out it was the navigation unit for which the wanted a whopping $2360 and $325 for labor! I found a reconditioned one online at Payne Volkswagen for $1600, so I ordered that unit and had the dealer install it as they also had to program it. In the end the only charged $60 for the labor and programming which was nice. $1600 for a reconditioned unit is still extremely pricey, they probably repair the unit for $100 or so but they can get away with charging a lot as a new unit is way more expensive, I tried to find a shop that could repair it for me but no luck there.

So in the end it cost me close to 2 grand (including the diagnostics) but everything is working again!

I do think that VW uses inferior parts for the navigation unit, you read a lot of stories where they break down, shouldn't happen in a premium VW as the Touareg!

 

Welp, removed the radio module at rear and got a good look at the p/n label and found several used units with the exact label except for date code. I won't buy a replacement just yet until I can test with fibre loopback to see if the display will at least turn on per swedishpolarbear mentions in his thread RNS 850 black screen and no 51 fuse blown...

Question:
Are these radio modules compatible between Audi & VW? The P/N label (attached here) on a used Audi radio matches my radio's label exactly except for the date code. All else is exactly the same. Any other considerations?

 

To my knowledge the tuner / amp box is the same.

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What did you do with the VCDS to trouble shoot?

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I just hooked it up and let it read all the fault codes. It did not indicate the navigation unit to be faulty, however it did say the radio could not be found and that there was an issue with the display. Both these units were perfectly fine. So much for VCDS being able to pinpoint the problem....

 

Thank you Frank. I've now removed the Radio tuner/amp and the Head unit Display and can confirm there's no fuses behind or around these modules. Disconnected and reconnected each hoping for a reset. No joy. Next I will remove the Nav unit in the glove box.
Here's the head unit label for reference;

 

Thank you Frank. I've now removed the Radio tuner/amp and the Head unit Display and can confirm there's no fuses behind or around these modules. Disconnected and reconnected each hoping for a reset. No joy. Next I will remove the Nav unit in the glove box.
Here's the head unit label for reference;

I did the same thing, I bypassed the radio with a fiber optic loop but VCDS still did not indicate the navigation unit to be at fault. The only message I got was: <Display not found> which lead me to think the display was the problem. Since you need special tools to remove the display I decided to throw in the towel and bring it to the Volkswagen dealer for diagnostics. If VCDS would have pointed out that the navigation unit was at fault (which happens a lot!) it would have saved me a trip to the dealer and the diagnostic labor costs. Water under the bridge now, I am happy it is working correctly again. But I bet you have the same issue, so far all symptoms are the same as with mine.

Still, crazy that something so expensive on such a premium car goes wrong so often and after such a short lifespan! I am certain that in the Netherlands (where I am from) Volkswagen would have to pay for it, especially yours as it is only 4 years old. There is a law that stipulates that if a product breaks down before the reasonable lifespan that one may expect from it, the manufacturer is at fault and will have to pay for it, at least partially. Here in the good ol' US of A they say screw it, warranty is over and we don't give a rats ass that it broke down before the reasonable expected life span. It always surprises me that companies are not more lenient with these kind of issues, it is not that they struggle to make a profit ($17 billion in 2019 and still $10 billion in 2020!) and it would make a lot of people buy another one of their cars. It really is a shame as apart from this I really enjoy the Touareg, it is the best everyday car I ever owned and I love to drive it!

 

Ok. Removed the GPS Navigation Control Module . No fuses back there either and I didn't expect to find one either. Though some posts have suggested there might be. Nope.
Removing the glovebox was tricky. Removed all screws and the lamp but it remained hung up at the top. There was an integrated clip just off center to the right that had to be pried away from the dash.

This unit is priced at $1735 retail. I can imagine what the dealership is going to want if I buy from them. The Component Protection (CP) will require adaptation by the dealership if I don't buy from them. What a racket.
Now I have to decide on which module to buy between the Radio tuner/amp or the Nav Ctrl module.

Here's the label

 

All fuses should be in fuse panels. But there are multiple fuse panels in the vehicle.

With VCDS you have to go into the module that is bad and run tests that are prescribed from the website.

If you can't get into the module then you contact ross-com and ask for help.

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Thanks Troy.

BELIEVE IT OR NOT
The RNS850 is back on line! Yay!
Here's What I did:
1.) Removed & reinstalled the Radio tuner/amp. All connections looked good, no trouble found. Tested - failed with blank screen.
2.) Removed & reinstalled the Display module. The connection looked good, no trouble found. Tested - failed with blank screen.
3.) Removed & reinstalled the Nav Ctrl module (Infotainment Center). All connections looked good, no trouble found. Tested OK! Just like that.

Moral of the story is that a hard reset by virtue of unplugging the Nav Control Module cleared what ever problem was there.

Another believe it or not is that I had never had the occasion to swing down the Infotainment Unit (Nav Ctrl Unit) before. In fact I didn't even know it was there until I pulled on that Yellow Pull Tab with the musical note on it. Kinda glad I ran into this problem -before- attempting the firmware & map update. That's next.

 

Thanks Troy.

BELIEVE IT OR NOT
The RNS850 is back on line! Yay!
Here's What I did:
1.) Removed & reinstalled the Radio tuner/amp. All connections looked good, no trouble found. Tested - failed with blank screen.
2.) Removed & reinstalled the Display module. The connection looked good, no trouble found. Tested - failed with blank screen.
3.) Removed & reinstalled the Nav Ctrl module (Infotainment Center). All connections looked good, no trouble found. Tested OK! Just like that.

Moral of the story is that a hard reset by virtue of unplugging the Nav Control Module cleared what ever problem was there.

Another believe it or not is that I had never had the occasion to swing down the Infotainment Unit (Nav Ctrl Unit) before. In fact I didn't even know it was there until I pulled on that Yellow Pull Tab with the musical note on it. Kinda glad I ran into this problem -before- attempting the firmware & map update. That's next.

/Congratulations, that just saved you a ton of money!

 

I have a dead unit. It was totally fine when I pulled it to install a stolen (Pheonix automotive) android system. Long story.. couple scumbags involved but ultimately my fault for trusting a fellow TDI guy. The android system didn't work, I know... shocker. So reinstalled OEM system. DVD in glovebox, monitor in the center. Everything is dead. nothing happening. VCDS says it can't be reached. Where do I start? I hear tales of three fuses to check. I'm only aware of 2.
position 47- Control unit 1 for information electronics -J794- Display unit for front information display and operating unit control unit -J685-
and position 51-radio. Both are confirmed good.

Is the third in the rear passenger corner near the amp?

 

I have a dead unit. It was totally fine when I pulled it to install a stolen (Pheonix automotive) android system. Long story.. couple scumbags involved but ultimately my fault for trusting a fellow TDI guy. The android system didn't work, I know... shocker. So reinstalled OEM system. DVD in glovebox, monitor in the center. Everything is dead. nothing happening. VCDS says it can't be reached. Where do I start? I hear tales of three fuses to check. I'm only aware of 2.
position 47- Control unit 1 for information electronics -J794- Display unit for front information display and operating unit control unit -J685-
and position 51-radio. Both are confirmed good.

Is the third in the rear passenger corner near the amp?

Look at the wiring diagrams for your specific vehicle.

There are 3 basic requirements when it comes to any module\component.
Power \ Ground \ Communication

The first thing to do when you can't reach something is to bust out WDs and check for the 3 basic requirements. (aka connections)

 

Ok, I will. I won't lie wiring diagrams aren't naturally easy for me. I've got some learning to do. But I'm willing to try that. Here's my first road block. There are 3 parts to the puzzle. Street names seem to be (display, Nav/Dvd, Amp). What does volkswagen actually call them on the diagrams? I want to make sure I'm looking at the correct units. And question about the fiber loop tool..... let's say i "bypass" the amp with the loop tool and the other stuff fires up. that means i found the problem. But can I assume that lack of power to a device/module prevents fiber optic signal from passing through it? I suppose that's what the test measures?

 

I can't follow.
You said the system was DEAD. Now you're saying street names are displayed! On what? The dead unit?
If it's displaying stuff, then you clearly have power. Street names or any other information displayed on the RNS850 screen will NOT be part of a wiring diagram..... that's not what wiring diagrams are for... they are for the electrical connection between components\systems\etc. Furthermore, you're now talking about the optical system..... I thought you were trying to find the correct fuses.

So, one thing at a time. What's the question?
Is it how to read a WD? If so, do you have a WD? If not, it doesn't matter if you can read it or not, because you don't have anything to read, so having the knowledge on how to do it is still useless.

There are VAG WDs which are harder to read\interpret, and you get them from the official manuals\erWin, and then there are simplified ones that are available from Mitchell, Alldata, etc.

It's nearly impossible to attempt to help you if we don't know what you are attempting to do.

Show up pictures, post VCDS scan, give us vehicle details, etc.

 

I'm sorry. I'll try this again. The display is black. Appears dead.

Correction, sorry for the confusion: There are 3 parts to the puzzle. Street names Common, nicknames of those three components seem to be (display, Nav/Dvd, Amp). What does volkswagen actually call them on the diagrams?

I assume the Radio (51) fuse protects what is commonly called the amp (in the rear right of the vehicle)
I assume the Display Unit (47) fuse protects that actual monitor, screen (in the center of the dash.)
Does this sound right? And if so, where is the fuse that protects the Nav/DVD player (In the glove box)?

The discussion about the fiber optics was not meant to derail the conversation. I was under the impression (maybe falsely) this was the best method to quickly isolate the problem.

I do have erwin diagrams. No worries there, I just suck at reading them; but I'm prepared to improve on that.

 

So I still don't know what vehicle you're working on.... I'll just assume it's a 2011+ for now.
Read this SSP on infotainment to answer a lot of your questions if my assumption is correct.
There's another SSP dedicated to reading VAG WDs, but you can also watch some videos on the subject if that's easier for you.
See here

Ross-Tech: Training

Once you review all that, ask your next question.

 

2013 TDI Lux

 

Alright, The SSP was very helpful. As were the links to the instructional video. Thank you for getting me pointed in the right direction. I tried to access the Radio with VCDS tonight and get the error, "No Response from Controller!". I'm guessing you'll say I need to check the system for 12V. Should I begin at the Radio in the rear, or the Nav in the glovebox, or somewhere else? Fuses 47 and 51 are good. As I understand it from what I'm reading fuse 47 is the nav and screen while 51 is the radio unit in the back.

 

Where did the SSP tell you the controller is located? That's the component VCDS is saying it can't reach.
What are the 3 basic requirements VCDS needs in order to communicate with a controller?
Confirm\fix those, and then you will be able to "reach it".

 

I'm thinking testing should start at the Can Bus Diangnostic gateway. It's near the left fuse box. Am I on the right trail? The three things we're looking for are power/ground/communication.

 

You retained the 3 things but you missed where the controller is. Read pg6 carefully.