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[Solved] Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec

kamil.k90 15780 19
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How can I restore the button backlight and automatic on/off function on an Audi A4 B6 Chorus 2 radio?

Yes — the problem was a disconnected cube/connector hidden behind the air-conditioning panel; once it was connected, the button backlight worked and the radio switched off with the key [#17027197] On this Chorus 2 unit, the backlight is tied to the car’s lights, so when the lights are on there should be 12 V on pin 6 of the power connector [#17018814] The radio’s automatic on/off is handled via CAN, not a separate ignition wire on the main connector [#17022237][#17022478] It was also advised to check that nobody had altered the power connectors and to verify the fuses [#17021820][#17018814]
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  • #1 17018788
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    Hello.
    I bought the Audi A4 B6 2004 station wagon last week.
    A chorus 2 radio is mounted in it. It was only in the evening that I noticed that there was no backlight on the panel buttons. The display works normally the same as the tiny TP button window. Is it possible to solve this problem?
    The problem is also that the radio does not turn on / off after starting / switching off the car.
    Thank you in advance for your reply and I apologize if there has ever been a similar problem discussed but I haven't found anything on the forum.
    Regards Kamil Kupiec
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    #2 17018814
    pdemski
    Level 20  
    Posts: 248
    Help: 36
    Rate: 71
    Board Language: polish
    On these radios, the backlight turns on together with the lights in the car. on the sixth pin of the power cube after switching on the lights must be 12V. Maybe someone was fumbling in the cables, you need to pull out the radio and check. It doesn't hurt to check the car's fuses.
    Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec
  • #3 17018823
    piotrek22101
    Level 39  
    Posts: 3323
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    Board Language: polish
    Chorus 2 has no backlight from the installation on a separate cable, neither the plus after the ignition. These signals follow Can'em if I remember correctly.
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    • Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec IMG_20180207_080919.png (111.57 KB) You must be logged in to download this attachment.
    • Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec 3992307600_1503244804.jpg (49.83 KB) You must be logged in to download this attachment.
  • #4 17019678
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    Thanks a lot ? only on the weekend I will have time to play with it. I hope it can be repaired somehow ? Should someone recommend some inexpensive radio that fits my car? There is a factory amplifier in the trunk.

    Added after 5 [hours] 1 [minutes]:

    And how to solve the problem with the radio turning on and off automatically?
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    #5 17021820
    pdemski
    Level 20  
    Posts: 248
    Help: 36
    Rate: 71
    Board Language: polish
    Check first that no one has been processing power cubes, because people can do various wonders, this could be your whole problem.
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  • #6 17022205
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    pdemski wrote:
    Check first that no one has been processing power cubes, because people can do various wonders, this could be your whole problem.

    I'm a little green but it's about the A pin 4 from turning on the ignition and pin 6 from the backlight? I apologize in advance for lack of knowledge in this field ?
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    #7 17022237
    pdemski
    Level 20  
    Posts: 248
    Help: 36
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    Board Language: polish
    Exactly.
  • #8 17022364
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    I took out the radio and this picture appeared. Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec
  • #9 17022405
    piotrek22101
    Level 39  
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    Brown speakers, black power supply. Minus brown, plus solid red with a strip, the third wire is K-line.
  • #10 17022423
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    piotrek22101 wrote:
    Brown speakers, black power supply. Minus brown, plus solid red with a strip, the third wire is K-line.

    Can you somehow get it backlight and turn it on automatically?
  • #11 17022443
    piotrek22101
    Level 39  
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    Is the radio sticker labeled? If it is as above (gray), then no. There should be a third cube.
  • #12 17022448
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    All in all, I didn't pay attention to the stickers. I'll have time to play with it over the weekend. In case you can, for example, pull the backlight and power supply from the ignition?
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  • #13 17022462
    piotrek22101
    Level 39  
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    You can pull, only the radio probably does not have these pins, you will see on the description.
  • #14 17022477
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    Can you make some extra pins? For example, solder them from the phone's side plug?
  • #15 17022478
    piotrek22101
    Level 39  
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    What will the pin give you, as no further electronics? Chorus 2 takes these signals from Can.
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  • #16 17022498
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    And how about connecting another radio? Eg what did you send? Will everything work properly with this wiring condition?
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    #17 17022519
    piotrek22101
    Level 39  
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    You need a plus after the ignition switch, adapter for the third cube if there is an amplifier. Backlight is an option, depending on the radio model.
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    #18 17022630
    rybeh
    Level 27  
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    This connection should work
    Attachments:
    • Audi A4 B6 2004 Wagon, Chorus 2 Radio: Button Illumination & Auto On/Off Issue - Kamil Kupiec oświetl.jpg (47.3 KB) You must be logged in to download this attachment.
  • #19 17024794
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    rybeh wrote:
    This connection should work


    The connection will fix the backlight or automatic on / off?
  • #20 17027197
    kamil.k90
    Level 8  
    Posts: 13
    Board Language: polish
    Subject to close? it turned out that there was no one cube connected, which hid behind the air conditioning panel. The backlight works, switching off after removing the key works. The current station and RDS are displayed next to the clocks.
    Thank you all for your help.
    Greettings and have a nice weekend!
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Topic summary

✨ The discussion revolves around an Audi A4 B6 2004 station wagon equipped with a Chorus 2 radio, which has issues with button illumination and automatic power on/off functionality. The user discovered that the radio's backlight does not activate with the vehicle's lights, and the radio fails to turn on or off with the ignition. Responses suggest checking the wiring, specifically the power connections at pin 4 for ignition and pin 6 for backlight, as well as verifying the car's fuses. It was noted that the Chorus 2 radio relies on CAN signals for these functions. Ultimately, the issue was resolved when the user found a disconnected connector behind the air conditioning panel, restoring both the backlight and the automatic power feature.
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FAQ

TL;DR: Audi A4 B6/Chorus 2 uses 3 ISO plugs; "There should be a third cube." If buttons are dark or auto on/off fails, pull the radio and verify that third plug is present and seated. [Elektroda, piotrek22101, post #17022443]

Why it matters: It restores night-time visibility and proper power behavior, improving safety and preventing battery drain.

Quick-Facts

Quick Facts

Why don’t my Audi A4 B6 Chorus 2 buttons light up but the display does?

Chorus 2 button lighting follows the vehicle light circuit. Measure 12 V at pin 6 when lights are on. Pull the radio and inspect the harness for tampering. Check the relevant fuses too. If pin 6 lacks 12 V with lights on, trace the wiring. [Elektroda, pdemski, post #17018814]

Why doesn’t the Chorus 2 turn on/off with the ignition?

Chorus 2 expects ignition and illumination states over CAN. If the CAN connector is missing, auto on/off will fail. Adding analog ignition or illumination wires will not restore these features. “Chorus 2 takes these signals from Can.” [Elektroda, piotrek22101, post #17022478]

What finally fixed this exact case from the forum?

One unplugged connector hid behind the climate panel. Reconnecting it restored backlight and ignition-controlled power. The cluster began showing station and RDS. That single plug caused both symptoms. [Elektroda, kamil.k90, post #17027197]

Which connector carries speakers, power, and diagnostic lines on A4 B6?

Brown plug is speakers. Black plug is power. Brown wire is ground. Red with a stripe is +12 V. The third wire noted is K-line. [Elektroda, piotrek22101, post #17022405]

Do I need a ‘third cube’ or adapter if my A4 has the factory trunk amplifier?

If your A4 has a factory trunk amplifier, plan for the third cube. You’ll also need an ignition-switched +12 V feed. Backlight input support depends on the new radio model. Use an adapter harness for the third cube as required. [Elektroda, piotrek22101, post #17022519]

Can I add extra pins or solder wires to force backlight and ACC on Chorus 2?

No. The radio lacks the electronics for those analog pins. It expects illumination and ignition states over CAN. Soldering extra pins will not help. “Chorus 2 takes these signals from Can.” [Elektroda, piotrek22101, post #17022478]

How can I quickly test the illumination feed (pin 6) with basic tools?

Use a digital multimeter.
  1. Pull the radio to access the power block.
  2. Turn on parking or headlamps.
  3. Measure between pin 6 and ground; expect about 12 V. If no 12 V, inspect fuses and the harness. [Elektroda, pdemski, post #17018814]

How do I check for miswired or modified power blocks?

Pull the radio and inspect the power cubes for modifications. Previous owners can do “various wonders” to these blocks. Restore the factory layout to resolve issues and ensure all connectors are seated. [Elektroda, pdemski, post #17021820]

Will an aftermarket head unit work in my A4 B6 with this wiring?

Yes, with the right harnessing. Provide a switched +12 V feed. Use an adapter for the third cube if the amplifier is present. Illumination support varies by aftermarket model. [Elektroda, piotrek22101, post #17022519]

Where is the missing connector likely hiding in an A4 B6?

Behind the HVAC (air conditioning) panel. In this case, one hidden “cube” was unplugged there. Reconnecting it restored lighting and ignition-linked power. [Elektroda, kamil.k90, post #17027197]

Why did the instrument cluster start showing RDS/station info after the fix?

The reattached third connector enabled data sharing to the cluster. After reconnection, the station and RDS appeared next to the clocks. [Elektroda, kamil.k90, post #17027197]

What is CAN bus, in one sentence?

Controller Area Network (CAN) is a robust multi-master automotive bus that lets electronic control units exchange data efficiently. [Controller Area Network]

What is the K-line in this Audi harness?

K-line is the single-wire diagnostic communication line specified by ISO 9141-2 used for vehicle diagnostics. [ISO 9141-2]
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