# 1998 Audi A6 can not communicate via OBD2 port



## bavareze (Sep 15, 2009)

Hello,
My 1999 Audi A6 with 2.8V6 engine works just fine, no warning lights on.
I tried connecting to the car with a generic OBD2 tool. I got communication error message.
Then i tried using VAG-COM K2 cable that i have. Still not working. I went to options -> test and i saw i have:
K1 - short to ground
K2 - OK
CAN - not present.
i assume the K1 should be also OK. where should i start troubleshooting?
i checked fuse 12 (DLC) and it is ok. my stereo is OEM, not aftermarket.
thanks,
~B 


_Modified by bavareze at 3:02 AM 11-3-2009_


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## Dana @ Ross-Tech (Sep 15, 2009)

*Re: 1998 Audi A6 can not communicate via OBD2 port (bavareze)*

Yes, the K1 should be OK. Any installed control module can crash the K line as well as an actual shorted wire. 
The ABS modules are notorious from that era, possibly start there. To rule a module out, unplug it and attempt communication or Test the interface again with VCDS. Refer to wiring diagrams and systematically unplug each one until they have all been eliminated as culprits. (You may want to leave the Airbag module alone, this is the least likely and a dangerous one to play with.) The next two I would go after are the TCM & Conv. / Central locking, due to the location under the carpet and noted water leaks.
You mentioned the radio is OEM, but is it the factory installed unit or has it been replaced? An incorrect OEM radio can also short a K line.


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## Uwe (Jan 16, 2000)

*Re: 1998 Audi A6 can not communicate via OBD2 port (bavareze)*

Does the radio work? The stock radios in those cars will keep the K-Line at ground if they don't get any power at all.
-Uwe-


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## bavareze (Sep 15, 2009)

*Re: 1998 Audi A6 can not communicate via OBD2 port (Uwe)*

radio works fine.
so i will remove in this order:
Radio
ABS
TCM (what is TCM?)
ECU
and then whatever i see.
i will attempt to remove the modules using the wire diagram. i have passat B5 manual, i hope this car is similar enough...
thanks,
~B


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## Uwe (Jan 16, 2000)

*Re: 1998 Audi A6 can not communicate via OBD2 port (bavareze)*

TCM is Transmission Control Module.
-Uwe-


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## bavareze (Sep 15, 2009)

*Re: 1998 Audi A6 can not communicate via OBD2 port (Uwe)*

i got some news.
i was able to locate the module that was holding one of the two K lines short to ground. it was the radio.
now, without the radio, both K1 and K2 are diagnosed as "OK".
however, when i am trying to connect with my KII interface, the result is "unable to communicate with controller", no matter what controller i am trying (engine, abs, auto trans etc)
other than that, car works like a dream, no warning lights in dash and fuse 12 is ok.
suggestions?
thanks,
~B


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## Dana @ Ross-Tech (Sep 15, 2009)

*Re: 1998 Audi A6 can not communicate via OBD2 port (bavareze)*

You mentioned that there was no communication with a generic OBD2 tool. Can you try that scanner again to verify no communication to the Engine? Or try your KII (and PC configuration) on another non CAN VW or Audi.
Have you unplugged the ABS module to check communicate to the Engine, Trans, Etc.? 
What are the details on the PC including the brand, model, OS, Etc.. You can take a look here regarding communication issues http://www.ross-tech.com/vag-com/faq_2.html#2.4
I see that you recently purchased from us. You are eligible for tech support. Please feel free to call if the suggestions here aren't getting you anywhere.


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## bavareze (Sep 15, 2009)

*Re: 1998 Audi A6 can not communicate via OBD2 port (Dana @ Ross-Tech)*

thanks for your response.
my pc is IBM Thinkpad X60 running XP. This machine with KII interface works fine with other VW that i have. Also, my OBD2 tool works fine with other cars but does not work with this Audi.
so obviously the problem is with the audi itself.
until now i have only removed the stereo. after that, K1 changed status from SHORT TO GROUND to OK so i thought that's all i need to do. I will try removing more and i will post the results once i get anything.


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