I've spent a few days trying to figure out why I can't read, flash, or log my 01 Allroad. My car is a manual swap car and has a late APB harness adapted to the earlier APB chassis harness (the firewall connectors are different).
The ECU bench flashed just fine, but on the car, pulling the radio or cluster fuses did not work. Pulling the cluster and radio entirely did not work. VAG-COM worked, but the ECU was simply not responding to the init.
An additional odd symptom was that I had a persistent DTC for lack of ECU communications with the instrument cluster.
My car has an Arnott coilover conversion on it that was not installed correctly - they simply unplugged the leveling computer and did not install the "eliminator" portion of the kit, as outlined on the last few pages here:
http://arnottinfo.com/manuals/C-2718.pdfSuffice to say, I plugged the module back in, and suddenly I could read, flash, and log. The instrument cluster dtc for no ECU communications disappeared as well. Obviously the dash is lit up for the air suspension missing, but I can deal with that until I can find a set of bags to throw back on it.
In any case I felt posting this information might be useful to somebody who experiences the same problem. My guess is that the k-line requires termination?