Okay I've been through the ringer with this thing. I've owned the car for a little over a week now. The radio wasn't working when I bought it and it had a check engine light on. Car runs strong and no other issues are present. Here's what I have tried thus far. Checked all fuses, pulled the stock radio out to find the 7.5 amp fuse was blown and replaced it. Checked the code, no luck. The head unit still didn't work after the fuse change so I ordered a used unit off ebay got it and installed it today. The radio works fine now and that bose system sounds great for a factory set up. Tried to check the code again and still no connectivity. Unplugged the ABS module and tried scanning still no change. Any other ideas on what to try next? unhook the battery for awhile? I've tried a Snap-on scanner as well as two different Actron scanners via AAP and my own. Now the guy I bought the car from said he finally got the Snap-on scanner to read the code once but when he went to do a run diagnosis it wouldn't connect again and he didn't get a chance to write down the DTC (Prior to me owning the car). I haven't tried the k-line voltage test yet but would I need to considering the Head Unit is stock?

 

are you using vag-com? what cable?