I recently attempted to install an AUX cable into my 2004 facelift 156 2.0 JTS fitted with the standard Blaupunkt head unit with the single slot CD player (no changer).
Blaupunkt ISO 8 polig für Klinke 3,5mm Adapter: Amazon.de: Navigation
I read through other threads on the forum advising that once the cable was plugged in, to hold the SRC button to switch to the AUX input, after many tries I could never manage to get it working and the head unit continued to display a NO CD message. I then read a thread showing how to short the data pins to fool the head unit into thinking a CD Changer was installed. However after shorting these pins the head unit continued to display the NO CD message after switching modes with the SRC button. The AUX cable should have had signal as I was playing music through it while switching modes with SRC. The only other cause of the problem which I know of could be the firmware of the radio. On the radio sticker it says that the firmware version is 2.08.
Any ideas on how I can get it working? Thanks in advance