I have asked for help before, but now I have more information.
I have been trying to pass the emissions test, but the guys can't get any communication link with the OBD connector.
I know that it is getting the proper power and ground. I know that the previous owner had played with the Radio (I have the BOSE system) and it wasn't working because of a fuse (I still need to get the code).
I've read that installing an after-market radio can interfere with the k line messing up the communication with the OBD. Like I said, I have an stock radio, but could the way it is wired interfere with the OBD?
Just as a note, if it means anything, I get a "check engine" light and a "air bag light", too.

Anyone have had a similar problem?
Any suggestions?
I'll appreciate your help.

 

if the radio is not functional even if it is installed that still might give you problems. it could be miswired.

 

When I bought the car the radio wasn't working. After trying to pass the emissions test twice I took the car to a mechanic who hasn't been able to find the problem (I just found out about the after market radio and the k line, so I haven't mentioned that possible cause to him). He pulled out the radio and replaced the fuse and now the radio asks for the code. Could it be miswired even if it turns on asking for the code?
What if I completely disconnect the radio or remove it's fuse from the dashboard?

 

the radio needs to be in there for the K-line circuit to be complete. just pull the radio out and look at the connectors, if they are the stock connectors that dont look all hacked up then they should be fine (i think there are 3 separate connectors that plug into the back, plus antenna). if the radio is working but just in safe mode, it shouldnt prevent the OBD port from working. you should try and fiigure out what the previous owner did to it.

 

I'm going to check it out later today and I'll let you know!
Thanks!

 

Well, the OBD works now!
I cleaned up the HVAC controls, got the radio working and the OBD works. I got a couple of codes when running the test (which I'm about to post to see if I can get some more help), but at least I made some progress.
Thanks for your help!

 

I am also having a similar issue. I am unable to read any codes from the odb connector on my audi tt 2001. My instrument cluster has been faulty for years (fuel gauge, and other sensors are misreading) but was always able to read the odb codes. Not sure what this could be. Any ideas? How did you clean up the HVAC controls? Any help would be appreciated.

 

If I remember correctly my problem was a fuse in the radio, so I just replaced the fuse.
To clean the HVAC controls I took out the radio and the AC/HVAC controls and used some cleaning spray. That did it for me!

Good luck!

 

I am having a similar problem. I bought my 01 audi a4 quatrro 1.8t in sept 2014 it was already inspected. I had a new radio put in it by a professional. I took it for inspection and it failed because of a communication problem. My abs light is on but they said it shouldn't effect emisions. They pretty much told me my car had no rpm.. i dont understand since my rpm gauge works fine.. does anyone have any ideas? I called a dealer and they want 95.00 an hour to see what the problem is

 

After tune up (coils and spark plugs) my car 2001 Audi TT quattro 180hp will not start. After so many cranks my Battery started to drain. I tried jumping to my Nissan 2014 Murano and still car will not start. Tried removing radio fuse due to aftermarket Alpine radio (which has been working perfect before attempting tuneup) and nothing. Also tried removing the ABS fuse and all my car does is try to start as if there is no gas (Tank almost full). I should mention when ignition is turned I can hear a noise which I am assuming the gas pump priming. Car has been running and starting perfect before attempting tuneup! WTF..now I can't read fault codes because scanner can't read from odb port which displays "No Link" error! Please help.
Update: Also noticed my CEL does does not come on, found fuse #10 is blown which has something to do with info from coils and fuel pressure (read that in another post) so I will replace fuse, then I will put the OEM coils back on (ebay performance coils may have to strong of a signal ) therefore blown fuse, cross my fingers! Hopefully I can get a reading from the obd port.
Update. Replaced blown fuse and original coils now car starts up perfect on first attempt. The performance ignition coils kept blowing fuse #10. Stick with OEM coils!