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Hi y'all! I am at my wits end and looking for help. I now have 4 ABS units for my C5 RS6 and none work. Last one came in from the UK and that one shows fewer faults than others. The most persistent fault is failure to register Left Front sensor. My mechanic traced all wiring, checked pins, checked resistance, tried a new sensor - nothing, unit refuses to recognize left front sensor even though electrically, there is nothing wrong with it. Other units had issues with registering other sensors as well - the new one sees other 3 (which is a progress) but not left front. I am not buying another sensor and I am not sending ABS unit to be remanufactured - again. Car drives just fine, but I can't register it with my dash lit up like a x-mas tree and it is worth more in parts than whole. But I do so want to keep it! Any suggestions are greatly appreciated. Thank you!

You can open up an old unit and see what’s been done to the tiny gold wires in gel that are the point of failure for these units. I personally haven’t had success repairing them.

I would really like to know how to reprogram a new unit from a different car. They are all (Bosch 5.7) so similar, not to say identical mechanically whether they are from
BMW or Audi or whatever model.

There really isn’t much of a solution than sending them for repair and hoping for the best. It’s crap I know.

Who have you sent them away to be repaired/checked to?

Seems odd if your having multiple modules that are not recognising the sensors on the car. 100% sure you have the correct PN module?

Motorsport ABS unit maybe? Not sure whether it would help with dash lights though.

Bosch do a kit.

https://www.bosch-motorsport.com/produc ... bs-m5-kit/

Wow. I bet that’s not cheap. Also it won’t do the ESP I’m guessing. Cool though.

Would imagine itll be harder to get that to integrate with the cars system than to make the OEM system work.

Thank you all for chiming in.

Yea, re Bosch kit, at this time I am not sure I want to through that kind of money at the car, especially since it is not known if it will work with my CPU. I may end up with an even more expensive collection of parts I cannot register to drive.

@felix2566 - I am not sure I want to name names but 3 of the 4 units were sent to 2 different guys. One of them - twice. That one worked for a couple years the first time it came back, but not the second. I am working with one of the guys right now, he is trying to help me figure out what's going on. And yes, I am sure I have the right PN. Once, an allroad module showed up and that one almost destroyed the car - locked it up so tight wheels did not move. We have been very careful since. And, all ABS sensors were replaced and all pins in the connector checked for continuity. We also tried to play mix and match with pumps - no go.

Had a persistent fault on my ABS control module where it would always show a fault for the rear right sensor. Even after replacing the sensor and crossing connecting it with the left one.
Strangely I could see wheel speeds while using Vag Com.
I had these guys repair the module and it's been good ever since, touch wood.

https://www.ecutesting.com/product-cata ... amc004283/

These guys did a perfect repair on my ABS unit when it failed a few years ago, quick turnaround too for mine at least -

https://controlunits.co.uk/

https://controlunits.co.uk/audi-a6-abs-esp-pump-ecu-2/

Thank you, guys. I have only so far tried local guys here in the US. Maybe next step would be to send a unit overseas.

Another thumbs up here for ecutesting.com

Just talked to my mechanic. Everything checks out. Everything behaves as it should - when tested individually. But once everything is hooked up, LF sensor does not register. After some more brainstorming, one of the potential problems could be electrical feedback (for a lack of a better term) in the harness. Car is old and lived more than half its life in the snowbelt. Harness is indeed ratty. So, next step will be to hardwire sensor to the pins to see if bypassing the harness for LF sensor would fix the problem. And if it does... I have 3 units to sell since they are likely to be good and useful to someone! But we won't know until January. Thank you again all for feedback and if you have anything else to add or offer comments, by all means! Cheers and happy holidays!

ECU testing sorted my brake pressure sensor issue out.

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