dgpach

Hi, I have a 2000 A6 Quattro with a 4.2L. Whenever I try to attach an OBD II reader, I get a link error. The reader works great on my 2001 A4. When this happened about 4 months ago, my Indy said it was a faulty ABS module which took down the bus. He replaced the ABS module and said it was fine. But now it's back to not linking. What I've tried is to unplug one of the powertrain modules and then ose the OBD II to try to link. If it still won't link I plug the module back in and try another. So far I tried this with the ABS Module, the TCM, the radio head, the climate control head and the central locking module (under the drivers side floormat). I also swapped out the ECU. Still no link. It there a "comfort and convience" module and if so where is it?

Any additional things to try are greatly appreciated

Dana @ Ross-Tech

If you were using VCDS (VAG-COM Diagnostic System), there is a test for the K line as shown here: http://www.ross-tech.com/vcds/tour/o...reen.html#test

You could find someone with VCDS in your local area to scan this and test the K line.

Since you have a Central Locking module there is not a Central Convenience module equipped.

dgpach

Hi Dana, Thanks for your reply. It took longer to check since I went out and bought a Vag Com. Still the same issue. The Ross Tech Vag Com reports:

Port Status: OK
Interface: Found!
Type: Ross-Tech KII-USB
Version: 1.81
Status: Ready
K1: OK
K2: OK
CAN: Not Supported

So the initial test routine is OK, but Auto Scan can't find any modules and when I try to select any individual module directly, it went through multiple attempts and reported the controller not found.

I tried this same inteface and laptop on an Audi A4 (2001) and everything worked fine.

Any thoughts on what I'm missing here? I'm not sure what to test next.

Thanks for your help !!!

Dana @ Ross-Tech

Wow, you have already eliminated the most common modules that cause communication errors. Including:
-ABS Module
-TCM
-Radio
-Climate Control
-Central Locking
-ECU

Does anything not work properly that you would suspect a potential problem with? Examples including Level control, Xenon lights, Steering wheel controls.

Please look at this list of modules to see what your vehicle is equipped with and further rule out:
http://wiki.ross-tech.com/index.php/...lroad_%284B%29

I would not remove or disconnect the Airbag module. It is possible this module could be the cause, but I would leave this for last.

dgpach

Thanks your input continues to help me figure this out. So would I be correct that when I sttempted the auto scan, after choosing the vehicle identifier (based upon the 6th and 7th VIN digits) the numbers that Vag Com presented is a map to all of the modules which could affect the module communications? Could a failure of one of these take down the intra module communications? (Please briefly explain)

The answer to your question is yes. I'm getting funky shifts from my auto trans. Two possible reasons are low fluid (why I need the Vag Com to check the level) and customer support for the trans manufacturer said that there were issues where the trans couldn't communicate with the throttle position sensor and therefore couldn't set the clutch pressure properly (whether you're part throttle or wide open throttle). So rather than dropping many many $'s on a trans rebuild which might not solve the problem, I want to check these out first. I'm expecting that my new Vag Com will help. Other than that I have the typical instrument display lcd drop out, and an unknown Navigation unit. My Indy had suggested unplugging the two air bag connectors behind the kick panels prior to doing anything with the airbag module.

Again THANKS for your help

Dana @ Ross-Tech

Yes, a failure of one of these can take down the communication line. Your vehicle appears to be a "K" line system. This is a system that has all diagnostic capable modules tied into a single wire that ends up at pin 7 of the DLC (Scanner port). Your Options > Test results did not show K1 short to + or - but there is a problem. If this was a dead short on the actual K wire or a module, that should have shown. A flaky module can be intermittent and hard to find, as you know.

Yes, the numbers listed on the top of the AutoScan include any possible installed modules for that platform. The Wiki page shows the text to further explain (56 = Radio, etc.).

Based on the Navigation unit problem, I would go there and disconnect it (assuming that it is a separate unit and not integral w/ the radio). The battery should always be disconnected before the Airbag components or module is handled. There is a serious safety concerns with that one, please refer to a repair manual or have your shop do this if you are in question.

dgpach

Dana, I'm going to leave the airbag control module to the last, but I do have a question. The procedure tells the repairman to write down the code from the currently installed module to later update to the replacement module. Since I cant access the currently installed module to retrieve the code, will this be an issue for me if I have to go through this?

Thanks

Dana @ Ross-Tech

It's ideal to have a scan prior to a control module failure for this reason. If one of your modules needs replaced I believe the coding and adaptation values should be well documented in your repair manual, Ross-Tech Wiki, Label files, etc.

If you’re in doubt, post the scan when this vehicle is communicating properly

dgpach

Had some success today. Vehicle now connects, the problem was the interior motion control module. When I auto scanned, I had multiple faults from my engine ECU ( not recoded after swapping this out while doing my diagnostic search, NO faults for the auto trans, and of course multiple faults with the locking system since the module was disconnected. Many thanks for your support ( I found the tables for recoding) I'm going to have lots of fun with this Vag Com it's a cool tool. Also wish I hadn't wasted so much time with an EBay brand X knockoff

Dana @ Ross-Tech

I'm glad you got this car to communicate and wish you the best with your diagnosis!

I'm not sure if your Trans. supports a Kick down adaptation or not, but check out this page and perform a TBA shown in the second link.

http://www.ross-tech.com/vag-com/cars/autotrans.html

http://wiki.ross-tech.com/index.php/...ment_%28TBA%29

You'll need to resolve any ATF level issues and any faults (including coding) before the above procedures are performed.