Audi A3 8L: Chorus II Radio Problem (2003)

Hi!
My friend bought an A3 1.9 TDI PD with 74 kW, which originally came with an Audi Chorus II (cassette only). The connectors on the back are properly connected, but the lighting doesn't work, and the radio doesn't turn on or off with the ignition. I have to manually press the power button every time, which is annoying, and it also turns off after about an hour. The dealer says it's normal for this model because Audi cut costs... which is nonsense, because the radio manual definitely states something different. A second authorized VW/Audi workshop gave a quote of 200 euros without anyone even looking at the car or the radio, and they said that a car electrician would need to run a new positive cable for it to work. (But there doesn't seem to be a free pin on the radio's connector for a positive connection!?)
As far as I know, the Chorus II, as well as the Concert II, etc., are CAN bus controlled, meaning that the on/off signals are transmitted via the bus. According to the pinout, the CAN High and CAN Low lines are connected to the radio. Unfortunately, I don't have a wiring diagram, and I'm not really sure what else I could check. Oh, and the radio doesn't lose the saved radio stations, so it probably isn't a power supply issue when the ignition is off.
I'm grateful for any advice (my partner is considering investing 200 euros, which I think is probably more than necessary).
Best regards, Martin.

Hi,

Perhaps the previous owner had a different radio installed and only partially downgraded it for the sale.
When I had my A3, I had to rewire the DIN connector back then. I just remembered that.

Best regards, Rainer.

Well, the previous owner was an elderly lady, so it's possible she had a different radio installed, but that's unlikely. All the current connectors are original and fit perfectly with the radio; there are no adapters, no power drains, and no shrink tubing.
Best regards,
Martin

Hello!

Okay, so either check Rainer's wiring (make sure that terminal 30 is connected to the correct pin and that the "S" contact is from the ignition switch), and otherwise, check if there are 12V on the "S" contact when the ignition is turned on. This should serve as a signal line for the radio (at least, that's how it works with "normal" radios).

Best regards,

Here's the pinout diagram:
http://www.flother-online.de/audi-a3/bilder/Belegung_Concert.JPG
I've only connected the wiring harness twice: once to C1 (which isn't available because there's no Bose system) and once to C3 (which isn't available because there's no auto-changer). However, these are output connections, so I can't connect the ignition signal to them.
Best regards,
Martin

Hmm. Okay. It seems to be exactly as you suspected. It's probably controlled via CAN. Perhaps you can adjust some settings through coding? The fact that it shuts off after an hour suggests that it's not actually receiving the signal that the ignition is on. That's strange! But it's still possible that the switching signal from the ignition switch can't be routed to the CAN bus because it's defective...
Does the ventilation work when the ignition is in the "on" position?

It has happened before that the CAN-H and CAN-L lines were reversed. You could check that.

Edit:

@brezelmann01

As far as I know, the power-on signal comes from the body control module (BCM) or the comfort control module (CCM) via the CAN bus.

Okay, that's possible. However, it's still possible that the signal doesn't even reach the onboard network controller, I think?

An 8L model does not have a body control module (BCM), it never has, and it never will.

All other functions are working perfectly, including the interior lighting control (when the ignition is on, the lights are dimmed).

'Can anyone tell me the cable colors for High and Low on the CAN bus, or how I could measure them? I vaguely remember something from my school days (it's been a long time...) about the CAN bus having a resting voltage of -3V for the Low line and +3V for the High line. Is that correct? I have a multimeter, but unfortunately no oscilloscope anymore.'
Best regards,
Martin