if the ABS is working then the module is fine. you only replace the module if both lights are on.
if your ABS is activating for no reason as you come to a stop you have a bad ring gear, or a bad sensor. what is happening is one sensor is not giving the right reading, either reading slow or fast so the car activates the ABS. if you have the Vag, you can set to measuring blocks (I think) and it will show all 4 sensors speed, this only works up to 20mph so I suggest doing this in a empty mall parking lot, drive the car and do many stops and watch each speed to see if one is off. now you can pull the sensor and test it, or remove the axle to check the ring gear. you can also remove the sensor and with a good small flash light look inside the hole at the ring gear, slowly spin the axle and see is you can see a crack or gap in the gear. when they crack the gap will be almost double but it is very hard to see and best to remove the axle to inspect but after several revolutions I did notice where mine was busted, i grabbed a used axle for about $30 and replaced.
I would recommend testing each sensor with a OHm meter to confirm they are all good then start checking the axles.

 

Where are you located ? , got to forum for your state, and best try to find someone in your area that have VAGCOM cable, that can access the abs module , and tell what is wrong, if they can't access the ABS, means bad ABS module, if they can access abs module, then it is operation just they can check error codes and let you what problems you having, this way you can avoid headache and guessing and replace wrong parts

 

Thank you for the replies. I will hold off on the module for now then. I have a vag-com, however I purchased it off of eBay and it didn't come with the full suite of software, what I have access to is pretty limited. I'm starting to fear that I will have to find a decent shop to take a look at the brakes, which I'm sure wont be cheap. I am fairly mechanically inclined, however it's blizzarding here (Fargo, ND) most of the time lately and my garage is full of my wife's "stuff" and my motorcycle stuff that I need to get to storage. So I cannot easily work on my car, but it might get up to 20 and decent towards the weekend so maybe I can wrench on the driveway. I have never pulled an axle before, is this a pretty difficult job? I'm the kind of guy that will try most things on his own first, occasionally to end up dragging it to the shop later. But it's too damn cold to mess around if it's something I can't fix myself. Thanks again for the assistance.

 

I have read a few posts relative to your problem and one stands out in my thoughts, the "brake switch" and it's position or fault. I have looked at the Ebahn schematic and noticed that the brake switch has two switching poles, one normally open for the brake light/abs and the second pole normally closed for the vacuum vent valve. Before you do anything check the brake switch with a VOA "volt,ohm,amp" meter or vagcom in the abs module functions.

 

I drove the Audi last night for the first time in weeks. I have been driving my truck since the brake issue has made it sketchy. The last time I drove it was during a blizzard and I thought that it seemed a bit odd, like the rear brakes were sticking causing the car to slide sideways on straight-aways (like I had pulled the e-brake). This only happens occasionally. Well, I confirmed that last night. I was driving and the car was fine, the ABS wasn't acting up too bad either. Than after a while they started acting up again. And while driving home I felt my rear brakes lock and stay locked, causing my tail-end to kick out. I was able to get it under control, but noticed that it felt like the rear brakes were still holding as the car felt bogged down. Eventually it came out of it, but you could smell the brakes were hot. Does this add any insight to the issue?

 

my car did this at one time to on the front passenger .. the ABS should cause it to unlock . never lock up .. do you have the stability feature ? maybe this has something to do with it ?

 

I agree, the Abs, should relieve pressure not give pressure to the brakes.
I would bleed the brakes, and change the fluid you could have dirt causing a piston to lock up, also remove and clean the pads, if the car doesn't get driven much you could have rust build up and the pads sticking.

I assume it could be possible to have a bad ABS pump which is not releasing pressure when you let off the brakes. and again I would suggest changing your fluid. give it a good bleed to run the old fluid and any junk out thru the pump.

 

It's actually rust inside the rear hubs... as it floats around and comes in contact with the abs sensor it causes the sensor to mis-read and send the incorrect signal to the abs module. Thus while appling the brakes, the abs module thinks the rear end it sliding, but being the steering wheel is straight and the front wheels are spinning at the same rate. So it's causes the rear brakes to "stab". Basically, the differentional pressure regulating valve goes full bore to the rear brakes. Hence the jerking/stabbing of the rear brakes. Mine used to do this, it's rust inside the rear hubs due to snow. My car came from NY,NH area. Snowy... So I had the same lights, the results.. the owners unplugged the second of the three fuses in the abs system to eliminate the jerking. Also causes no communications that way. Plugged it back in and found out about the stabbing brakes... removed the rear sensors and found tons of rust. Cleaned the sensor and sucked up as much rust out of the hub as I could. Now what happens is the rust will fall in between the hub wall and the magnetic ring and "float" around while you drive. Occasionally I'll get the brake pedal falling out from under my foot, thats when I know the brakes are about to stab.. Just a gentle lift up off the pedal eliminates this stabbing effect. Haven't had the time to pull out both axles to fully clean the hubs and rings, but that is the main issue here.

Oh also after the fuses are all good, communications to abds module were restored.

Hopefully this helps someone later on.

 

UPDATE!!!!! Yes I know it's been months and months. But I've found the solution to the random relay clicking, Xenon headlights flickering, and lastly the famous rear brake random lock up!... Yes I've found it.


Turns out after long tests and many many nights of scratching the head at why the rear brakes kick on and headlights flicker due to some relay clicking when the brake pedal is released or throttle is feathered on the fwy. The culprit you ask, well that's the good ol' wheel bearing. And now you ask well what the hell does a stupid wheel bearing have to do with the brakes or even the damn headlights!

Well... EVERYTHING! That is when the wheel bearing begins to fail, what does it do? It begins to allow the axle to travel up, down, pretty much in every direction. And what does this do in turn to our equipment?? well that little abs ring inside that hub starts to rub against the inside of the CV housing (hub). When this happens it causes the ring to get chewed up and literally grind itself down. To the point that the wheel speed sensor can't always pick up the correct reading, thus falsely activating the rear brakes only and prematurely. I also tested how it reacts to the steering wheel due to the clock spring with angle sensor, it actually increases the chances of "brake stab", which is activation of brakes abruptly.

Now many of you are probably saying, well that's not true cuz vag-com says my wheel sensors read correctly all the time... Well.. YOUR WRONG! sorry... well no I'm not. But your still wrong very much so. And why, simple because my system I have in my car, I can read my wheels speed directly on my dis, and all my wheels say the same... speeds are match and are good. Now your gonna say well my ring was cracked... well no it isn't. My ring had just enough finger depth to read and work correctly most of the time. I'll post a picture of it... it's 3/4 worn down... yet still worked, oh also my sensor has been chewed up by the ring due to the bad wheel bearing. So all in all, my read outs all read correct. even tho I knew i had a bad ring. Either way I still had the problems constantly.

So the solution, many of you already know. Buy a new CV.... well once again we're right back to.. YOUR WRONG. I say it out of love. does that help? Anyways, I know I know... all of you are saying wtf!... well in fact buying a new cv to get a new ring is in fact mostly the only way to repair a "bad" ring. But not anymore...

No need to spend 85,95,100 dollars in new cv's or even axles as some of you had done that. I've got many of these rings and if anyone needs to replace one or more, then let me know.

The solution to getting your lights,brake system and random relay clicking. Is to replace that bad wheel bearing and the abs ring thats bad on that side. Then the all the systems will go back to normal. I've been click free, flicker free, and brake stab free for almost a week now... AND DAMN DOES IT FEEL FREAKIN NICE!!!!!!!

Send me a PM if ya need the replacement rings. Mind you, you wont find them anywhere... Germany sells them at $125 (75 euro) a piece (that's way to expensive, get them from me, much cheaper). And no one else anywhere has them. Trust me

 

Everyone is paying way too much for their computer rebuilds. I just bought one from ebay: http://cgi.ebay.com/ws/eBayISAPI.dll...m=380291789013

Worked great, they had it returned in under a week.

No affiliation, just a happy customer. If the post expires, they are Automotive Scientific Inc. Seller profile is ATE1234.

Just an FYI for those who find this thread while searching.

$53 is hard to beat!