A6 ABS fault
 

Hello!

About a year ago ABS and (!) light appeared in dash after riding though snow while snowstorm. So few weeks ago decided to deal with the problem and bought used one with same code and so on. So changed my ABS module and still same fault. After that had my original module soldered (that one has been opened before me), so I changed back to that one and STILL same fault. Connected my VAG-COM and if the ABS is connected program says "Interface not found". So decided to change the whole pump with the one I bought. After connecting it with car and my pc with car it finds the interface, but cant even connect to engine. Looked out fuses, everything seems to be okay. Took off the power plugs from battery to reset ECU. After that if I connected the VAG-COM it said again "Interface not found", so removed the ABS cable from the module and in finds the interface again.

So where the heck can be the problem ?

Car is Audi A6 C5 2,5Tdi '99, European Version.

Both modules are defective? What code did it throw originally after the snow storm?

Also, just because your problem happened after the storm, it leads me to believe you have an issue with a sensor that possibly could have gotten damaged.

Didn't diagnose it soon after the fault appeared, but if we did after changing the module, then it said it cant connect to the "ABS brakes", and if testing engine, it says:
18259 - Powertrain Data Bus : Missing Message from ABS controller
P0851 - 35-10 - - - Intermittent

Everything seems to point back to the ABS module. Do you have access to another car where you can test the modules?

Just tested cable on friend's A8 and it connected with ABS

Go to all four wheels and check the cables from the ABS sensor(s).
Also, consider testing ABS unit on another car.

But testing the module on another car means that those pump codes match ?

On another car if the ABS codes match you can test your abs module yes.
Awkwardly phrased…but the point is that Audi didn't make unique abs modules for each car…I don't know how many different ones.

Clearly you'll have to have some friend(s) faith to allow you to remove their abs module and install yours to test if the module can be communicated with. It takes a couple hours for the first time, you have to go in through the left front wheel well which involves removing the wheel and fender liner as a minimum. Also have to remove w/s washer reservoir screws and move the reservoir slightly out of the way.

BTW..the general indication of ABS module fails is a lit ABS and BRAKE light(s) on the instrument cluster. I'm not confident the ABS module is your problem.