The ABS in my C5 S6 occasionally does a strange fast grabbing as I come to a stop

[IbisB7stage2]

It only happens a few times a week. As I'm braking to a full stop and am under 5mph, the brakes seem to judder/vibrate for half a second, and I can feel it in the pedal.

The ABS and traction control lights will illuminate on the dash, but will be off next time I get in the car.

Anyone know what's going on or where I should start investigating?

[ShelbyM3]

Have you scanned the ABS Control Module when the lights come on? I’d start there. It probably has something to do with a wheel speed sensor or their wiring harnesses. VCDS may be able to point you in the direction of which corner is the culprit, probably a front, and then you can go from there.

I would get a random traction control light that pops on in my Project Dana, when she was on the road, when I took one specific corner on my commute and hit the fog line rub strip. I chalked it up to this. I’ll probably be following in your footsteps in a few months.


Sent from my iPhone using Audizine Forum

[A4Qwattro]

It's typically an issue with the wheel speed sensor ( could be bad, or metallic debris has covered the sensor head), or the tone ring on the cv axle has cracked o. You can check the measuring blocks with VCDS in real time to determine if the reading is bad, but it may require taking the axle out to inspect the tone ring and the sensor head for debris or damage.

[IbisB7stage2]

just did a scan.

00283 - ABS Wheel Speed Sensor; Front Left (G47)
30-00 - Open or Short to Plus

so wiring may have cracked/failed? would a dead sensor give this same error?

[02 A6 2.7T]

just did a scan.

00283 - ABS Wheel Speed Sensor; Front Left (G47)
30-00 - Open or Short to Plus

so wiring may have cracked/failed? would a dead sensor give this same error?

It's possible, but check for moisture/corrosion in the harness connector as a first step. A replacement sensor with harness starts around $20 here, and is cheap enough I have a new one in my tool box for diagnosing ABS faults in my C5 stable : https://www.rockauto.com/en/catalog/...ed+sensor,1912

[IbisB7stage2]

cool, thanks for the help chaps. I've got a solid list of what to look for. It'll be a minute before I can disassemble anything since my B7 is in the garage on jacks.

[jbain2]

]]stage;[emoji6][emoji[emoji6]][emoji[emoji6]]]cool, thanks for the help chaps. I've got a solid list of what to look for. It'll be a minute before I can disassemble anything since my B[emoji[emoji6]] is in the garage on jacks.

It’s an easy fix actually. Just need to pop the wheel off. Everything is accessible from there. I suspect you just have a bad sensor. The other issue to consider though unlikely would be a bad tone ring on the axle.


Sent from my iPhone using ]][emoji[emoji6]][emoji6][emoji[emoji6]][emoji6]]Audizine

[ShelbyM3]

just did a scan.

00283 - ABS Wheel Speed Sensor; Front Left (G47)
30-00 - Open or Short to Plus

so wiring may have cracked/failed? would a dead sensor give this same error?

I’m unsure if the code would change based on wiring versus failed sensor. You could try to unplug it and see if the code changes, but I suspect it won’t.
I mentioned wiring because I’ve read stories, the harness articulates with the uprights, and that area is exposed for 22+ years. Do a good visual inspection of the harness in the wheel well and check for any moisture ingress in the connector, like mentioned above. Check the pins at the connector for any corrosion, too.
When I had my axles out of my Project Dana, I sprayed the hubs with a degreaser and scrubbed them with a nylon brush. I also scrubbed the tone rings on the outter CV’s. Brake dust and road grime will build up in the hub, potentially corrode the tone ring on the end of the axles, build up on the wheel speed sensor tip, and make your signal wonky. If you want to go as far as removing your axle you could try to clean everything out really well and see if that improves things. With it appearing to be an intermittent and specific issue, and not a blatant failure, this could be the solution.

If you do need to remove the wheel speed sensor, use lots of penetrating oil and maybe let it soak for a day or so. Last thing you need is a broken fastener or the wheel speed sensor seizing into the hub. Posi-vibes


Sent from my iPhone using Audizine Forum