NotoriousGLU

I was looking through D4 threads for ABS repair service but couldn't find anything. By service I mean taking my ABS sensor and sending it to get it fixed. Can you provide any recommendations please? The module is acting up on my 2011 A8. Thanks.

MP4.2+6.0

You may be the first. From watching this same progression on the D3 vs. D2 when the D3 owners started having issues as they aged, you should thus dig out the D3 references that are now around. Get in touch with the shops to see if they are doing D4 modules yet. It's really not so much the specific model probably, but rather whether they are testing and repairing the relevant Bosch ABS generation used in your 2011.

Have you run a VCDS scan to find codes in it, especially the one that says "module defective"? You can run the self test on it with VCDS too, though I am reluctant to do that when I think it is healthy (unlike yours apparently).

NotoriousGLU

@MP4.2+6.0 I attached VCDS scan. The way the issue starts is on the speed above 45mph while on a highway... First, ESC system is flashing about two times (would make me think that sensors are reading wrong speed on the wheels) after there is a whole series of warnings coming on you will see in the scan info.

I installed brand new speed sensors on the car and it is still showing left front wheel sensor mechanical failure. When you look over to transmission codes it looks like ABS module is not communicating right way with transmission. therefore, my assumption is that module needs to be repaired (new one is about 1600 I don't feel like paying for new one lol).

How would you test the module through VCDS?

MP4.2+6.0

My reaction skimming through it is the codes scattered all around seem ultimately to come back to that left wheel sensor. Three ideas:

1. Check the sensor again. Be sure of course that your prior replacement part was correct, not damaged, etc. Maybe consider corner cases too like something got into the ring gear area--or whatever they call the teeth around the CV joint that the sensor reads when spinning. I would probably at least disassemble and spray brake cleaner into the sensor hole, if possible free spinning the drive axle to clean it all around. Also, look at outer CV joint on that side and general boot area to be sure there is no grease that has gotten out--cracked boot or otherwise. You usually see splotches of it on the inner part of the wheel barrel if a CV joint boot has issues.

2. Look at sensor wiring. Use Deoxit type contact cleaner. Consider running a continuity check on the wires from the sensor to the ABS unit. Will require a careful look at wiring diagram. If that sounds like too much, at least clean up connector and then consider advancing to #3.

3. Use the self test. Called an Output test in VCDS speak. See here to get general sense of them. There is one in ABS module. https://www.ross-tech.com/vcds/tour/out_test.php I discourage them in D3 if there are no issues, since owners have reported the test runs with no obvious code prior to test, and then can permanantly record an "ABS module defective" code. But it may be that is ultimately because...it is defective. Since you are considering replacing/rebuilding anyway, seems like nothing to lose and it may tell you something--either bad, or apparently not.

NotoriousGLU

@MP4.2+6.0 I have new wheel hubs and wheel bearing on the car. Initially when the ABS sensor "failed" according to the scan I assumed one of the mechanics working on my car made some grease mess. Before installing new ones I made sure there is no mechanical obstructions in the hole where sensor reside, for the sensor to read correct speed. When I check for the speed sensors are reading it looks like sensors are reading correct speed on all 4 corners. When I am doing testing non the functions are coming back as non responsive... See attached for the functions... So far I am leaning towards ABS module.