GIAudi

Replaced my ABS controller yesterday with a rebuilt one and now lights are out and no beeps, but now when I come to any stop, the ABS kicks in shortly after applying the brakes. Seems as if the sensors say the wheel is skidding. Any thoughts on this would be greatly appreciated.

Redneck Truck

That sounds terrifying. I don't know if the ABS wires are typical wires or I'd suggest a continuity tester or a tone generator. Also, inspect each ABS sensor where it mates up to the tone ring on the axle.

Why did you replace the original pump? Could it be that this was the issue that caused it to fail originally?

4Driver4

All wheels, or just one? Sensor(s) not seated? How long was the ABS unit bad? Check wheel speeds using VAG-COM

Johann2.7t

how can you do that?

is there a way to test which wheels is slipping when the esp comes on via vag?

4Driver4

VAG-COM measuring blocks show the measured speed at each wheel on the fly. You can even see them graphically.

GIAudi

Yeah, it is weird. I didn't replace the pump, just the typical electronics that go bad. It was bad for some time, but the unit was in great shape, no corrosion in or out. Sent to BBA Reman for the work. No beeps on startup and all seems fine until you hit the brakes. Starts braking action fine, then about 2-3 seconds after the ABS kicks in until the speed of car falls below the threshold of the unit. The pump continues to run after the car has stopped. Really weird. Just replaced all rotors, pads and even the sensors. If i cant figure it out I'll have to get it VAG'd. I just don't have a place even close to me.

4Driver4

There is nothing odd or weird here. This is a typical problem resulting from a dirty or not fully seated sensor, or a cracked tone ring. The clues are in your comments.

So there was plenty of time for other work to be done on the suspension or brakes that dislodged a sensor.

You could have created the issue doing the brake work.

Start by firmly pushing all sensors into their bores. If you still have the issue, start looking at measuring blocks in VAG-COM. Don't look for codes; there aren't any.

GIAudi

Alright starting with sensors. I will make sure they are fully seated. The tone ring is on the cv shaft I'm assuming so I will start with those items first. Could contamination on the tone ring cause this as well or would it be a mor persistent issue.

As a side, I took the car for a short drive and after a short time the yellow ABS light came on and remained so until shutdown. All pump running ceased. Turned car off, then light was gone and has not returned.

thejulex

On my A6 (C4 platform though) when the ABS system started malfunctioning it was actually a relay in ABS pump that crapped out. It caused ABS ECU to start malfunctioning and misbehaving and everything was pointing at ECU failure. But after ECU replacement there was no improvement. Comes out the ABS pump has two relays located behind plastic door and one of them was the culprit.

What I would do if I was in your place is I would measure the wheel speed first so that you know the readings are right, chances are one of your sensors is shot.