April

Since I had my car up in the air for last week or so, and the discussion of ABS sensors comes up once in a while, I thought I'd take a picture.

<img src="http://pictureposter.audiworld.com/3127/abs-1.jpg">

The item in the red circle is the sensor lead. Check that it is firmly connected and that the wires are not frayed.

The item circled in blue, is the sensor itself. It is usually positioned several millimeters from the striated disc (parallel to yellow squiggle) on the back of the hub. Check that clearance is set to spec and that the disc is free of debris.

Sometimes road crud can kick up and knock the sensor out of alignment or loosen the lead. Similarly, if brake or suspension work is done, those items can get out of adjustment. If your ABS light comes on, it's often the easiest thing to check (although in the case of your Audis, the brake disc will be on the hub as well, the ABS stuff will be behind it).

meq123

Cool! Thanks. I assume that's your Alfa?

4Driver4

if you run your brake pads down to the metal. This can also cause ABS issues.

S4_Cinci (I S'edTFA)

But then I always seem to get this metallic taste for several days afterwards when brushing...it pays to keep the sensors clean! Thanks for the primer April! Another reason why AW is the best.

April

Yup! All patched up now and ready to go tearing around:-)

Kris Hansen

in fact, the 'toothed' ring is more like those rumble strips on the edge of the highway than a gear like on your car. The whole thing is buried in the bearing carrier/upright/knuckle. You can't see the toothed ring with the axle in place. The sensor probe is recessed into the upright, there is almost no way brake particles can get to it, though, mud/dirt etc can work it's way in there.

April

Execution is considerably more advanced on the Audis ;-)

Kris Hansen

<img src="http://www.kris-hansen.com/Audi/images/audiworld/frontabssensor.jpg">

<img src="http://www.kris-hansen.com/Audi/images/audiworld/rearabssensor.jpg">

April

Ah, thank you! Same concept, just less likely to have debris enter the ring assembly.