# Trick : How to activate the AUX function on a RCD300



## macgyver216 (Mar 26, 2007)

*Trick : You can activate the AUXILARY AUDIO INPUT function on a RCD300 !!*

This may interest you. 
I have an European Passat B6 with an RCD300 (8 Speakers, large display in the instrument cluster), that have an OEM Auxilary Audio input in gloves box.
When I press twice the CD switch, AUX appears on the display.
I removed this AUX few month ago because I installed an USB Xcarlink instead of it.
Last night, I read the radio codage with VAG.COM, it was 
0040401 , this coding doesn't exist on the label file.
My RCD300 have actually a fault code : Radio bad coded. May be because i removed the AUX and installed the xcarlink. But evrything works good.
So I suppose if you change the coding of an RCD300 to my coding, you can activate this hidden function.
The OEM AUX input is not hard at all to made: it have just a female jack, two resistors and three wires plugged on the CD charger connector behind the radio.
I’ll try to take the resistors values when I’ll have some time.

_Modified by macgyver216 at 7:39 PM 7-11-2008_


_Modified by macgyver216 at 8:56 PM 7-11-2008_


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## bourasnik (Dec 31, 2007)

*Re: Trick : How to activate the AUX function on a RCD300 (macgyver216)*

It sounds very interesting. We are waiting.


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## macgyver216 (Mar 26, 2007)

*Re: Trick : How to activate the AUX function on a RCD300 (bourasnik)*

Ok, here the schematic of the connector, very easy to made.








I'm trying to find th connections behind the radio.


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## macgyver216 (Mar 26, 2007)

*Re: Trick : How to activate the AUX function on a RCD300 (macgyver216)*

Ok here the schematic of the CD Charger connector behind the radio.
I found this photo in a French forum.








I suppose that the AUX connector must be plugged in CD Left, CD right and Ground pins (color pins)
I have te check this on my car, but i don't have time to remove the radio, my AUX wires (that connect the AUX to the radio) are still mounted in the car.
May be the detection of the two resistors by the radio are sudfficient to active the AUX function without coding change ?!
I hope that it can be helpful for you


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## Serv_electronics (Jul 21, 2008)

I have tried "the 2 resistor" method, my rcd 300 don't recognize anything (aux in)







Any ideeas?


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## Theresias (Feb 11, 2004)

The RCD300 is available from different supplier companies, not all of them do support the AUX-IN.


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## macgyver216 (Mar 26, 2007)

In fact, my RCD 300 is not a Blaupunkt, but a Grundig.


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## Serv_electronics (Jul 21, 2008)

There must be a method to activate the aux in :-??


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## pbogdan (Jul 23, 2008)

I have a brand new VW Golf with an AUX-in in the middle console and the problem is that it doesn't work at all. (the RCD 300 doesn't recognize the AUX-in)
Where is the problem? isn't activated? or not connected?


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## Serv_electronics (Jul 21, 2008)

Ai incercat asta? Have u tried this?
"When I press twice the CD switch, AUX appears on the display."


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## pbogdan (Jul 23, 2008)

I've tried everything...... I pressed once, twice, with the CD insinde-outside, with audio signal on AUX-in , without.....


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## macgyver216 (Mar 26, 2007)

*Re: (pbogdan)*

remove your radio and take a look, may be the AUX connector is simply not plugged.


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## Serv_electronics (Jul 21, 2008)

*Re: (macgyver216)*

once you find out how to activate the aux in please let us know.. I think that u have to modify sonething with the VAG-com.


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## Electron1948 (Feb 5, 2009)

*Re: Trick : How to activate the AUX function on a RCD300 (macgyver216)*

I have a Grundig RCD300 with MP3 CD facility. I tried making up the cable described (with two resistors) and pressing the CD button twice.
All I get are two messages on the LCD: "No CD" and then "No CDC"








It seems that the Aux-in port needs to be enabled somehow. I have a contact in the motor trade - I'll see if I can find out how it's done.


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## Theresias (Feb 11, 2004)

Please read my postings above, it cannot be enabled on all units - thats a hardware problem or similar. Nothing a diagnostic tool can solve.


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## Electron1948 (Feb 5, 2009)

*Re: (Theresias)*

Hi Theresias,
Well 'macgyver216' who posted the 'solution' said he had a Grundig RCD300 and so do I so I thought it was worth a try. There is obviously something more required.
I have details of a homebrew CD Changer Emulator so I will maybe have to build that and try it - a good thing I'm an electronics engineer.


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## Theresias (Feb 11, 2004)

*Re: (Electron1948)*

As said, some may, others may not. Simple as that. Since claim to be "skilled", why not open the thing up and check whats missing hardware wise...


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## Electron1948 (Feb 5, 2009)

*Re: (Theresias)*

On modern electronics you are likely to get nowhere without a full service manual - however skilled. I've fixed all sorts of radios, surface mount technology and all, _with the diagrams to hand_. The added problem with these things is that they have computers in them and there is no knowing what they do. Looking at another site there is a suggestion that the VW diagnostics software for the car can make these changes - but that cost several hundred US$


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## Theresias (Feb 11, 2004)

*Re: (Electron1948)*

What site are you referring to? Got a link?
From experience (I do have a VAS here as well), neither VCDS nor the VAS is able to do what you're looking for.


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## Electron1948 (Feb 5, 2009)

*Re: (Theresias)*

Theresias,
I had to hunt around again but then remembered to look again at the links on your email sig!
This page:
http://www.ross-tech.com/vag-c....html
says:
"So you can set various options, like whether a CD player is connected, whether there's an amplified or conventional antenna, and so on. In addition, these radios constantly monitor their speaker outputs and if you have an open or short circuit to one of the speakers, even a momentary one, they will record a fault code."
and this page:
http://www.ross-tech.com/vag-c....html
has a table with these entries:
2005.5-2009 Golf/GTI/Jetta/Rabbit:
47 Sound System (CAN, if equipped)
56 Radio (CAN, if equipped)
I may be totally wrong but it looks hopeful - clutching at straws maybe?
Electron


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## Theresias (Feb 11, 2004)

Definitly straws here... You're mising things up a little, the applications page only lists installed diagnostic capable control modules while the aftermarket radio page only refers to the standard coding table but technically the option you look for simply doesn't exist.
Don't take this the wrong way but I have no intention and time for explaining ever and ever again and in all detail why something isn't possible, in some cases a simple "no, doesn't work" has to suffice.


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## Electron1948 (Feb 5, 2009)

*Re: (Theresias)*

Theresis,
No problem at all in accepting the "No, doesn't work"







. Nice to 'meet' with you and maybe our exchange will help somebody else or trigger a thought somewhere that will solve the problem. Meantime I'm bidding for broken Ipods on Ebay!
Thanks again for your help.
Electron


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## AuroraAutoTechnology (Jul 19, 2013)

Sorry but a lot of you are WRONG in this thread, the later RCD300 (Including Grundig) are even easier to put AUX input, they can be programmed with VCDS. No resistor needed.

Maybe some hope to some of you, I saw this thread when I was looking at something else and thought I would share this.

To enable AUX input on 2007+ unit do the following.

With VCDS:

VCDS, RADIO, Coding and change last digit to 1 "Do It"

Then turn radio on and off or exit VCDS, check its working by pressing CD once if no CD inserted or CD twice if inserted. Should say AUX, if it does then go to step 2, if not you have done something wrong, check you coded right digit.

Radio wiring:

Find CD changer socket on radio, PIN 8 Aux in Left, PIN 9 Aux in Right, PIN 2 Ground.

I solder directly to the pins on Radio, however I have £500 soldering iron and am an electronics engineer lol, but you could buy generic Blaupunkt cable or FAKRA (Quadlock) cd changer plug and make your own.

Ignore my jumper wires, they are for +/- 12v, SAFE and speaker to test on bench.

Pics:







Let me know if this helps.


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## raresvintea (Nov 6, 2012)

I've tried coding, put the cable, the menu appears but No sound while playing music trought 3.5mm jack. Any ideea? All the connections are good. I have a unit like upper one but with mp3.


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## RichardSEL (Apr 5, 2010)

If you post your Autoscan, experts in here will be able to see what modules you have and their settings
What radio?


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## raresvintea (Nov 6, 2012)

In coding option in module 56-Radio, for the last digit the options were +1 antenna, +2cd changer +4 anything else..
I tried add +2 but the option didn't appear, when i've put +1 option appeared. I don't remember who is the producer of the radio. 
Option appeared when i press twice the cd button, but when i pus signal from a phone nothing is amplified through speakers....


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## stefanokan (Apr 27, 2015)

*VCDS-Lite doesn't connect to channel 56-Radio*

VCDS-Lite V1.2 connects correctly to channel 01-Engine, but it gives timeout trying to connect the channel 56-Radio.
So i'm not able to change the coding to enable AUX in my VW Touran year 2008 with RCD 300.
Any help would be highly appreciated.


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## bibanu76 (May 2, 2016)

*Aux 2 Resistor squeme*

Hello.
Do you still have the squeme for the RCD300 (no mp3, no +) aux cable ?
Thank you.


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## bjorfeldt (Oct 15, 2017)

*Scheme for resistors to RCD300*

@AuroraAutoTechnology! Stumbled upon your post about fixing an aux connection on the RCD300. Changed the coding but can't see the scheme you posted. You don't happen to have it still and are willing to share


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