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
- Chorus 2 illumination/ACC states are delivered via CAN, not added analog pins; soldering extra pins won’t help. [Elektroda, piotrek22101, post #17022478]
- Illumination check: pin 6 should read about 12 V with lights on; verify with a meter. [Elektroda, pdemski, post #17018814]
- Factory amp present? You’ll need a third-cube adapter and a switched +12 V for aftermarket units. [Elektroda, piotrek22101, post #17022519]
- Harness basics: brown plug = speakers; black = power; brown wire = ground; red/stripe = +12 V; third wire = K-line. [Elektroda, piotrek22101, post #17022405]
- In this case, one hidden connector behind the HVAC was unplugged; reconnecting restored backlight, auto on/off, and cluster RDS. [Elektroda, kamil.k90, post #17027197]
Quick Facts
- Chorus 2 illumination/ACC states are delivered via CAN, not added analog pins; soldering extra pins won’t help. [Elektroda, piotrek22101, post #17022478]
- Illumination check: pin 6 should read about 12 V with lights on; verify with a meter. [Elektroda, pdemski, post #17018814]
- Factory amp present? You’ll need a third-cube adapter and a switched +12 V for aftermarket units. [Elektroda, piotrek22101, post #17022519]
- Harness basics: brown plug = speakers; black = power; brown wire = ground; red/stripe = +12 V; third wire = K-line. [Elektroda, piotrek22101, post #17022405]
- In this case, one hidden connector behind the HVAC was unplugged; reconnecting restored backlight, auto on/off, and cluster RDS. [Elektroda, kamil.k90, post #17027197]
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.
- Pull the radio to access the power block.
- Turn on parking or headlamps.
- 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]
