ABS error

Hello.
Wir hatten gerade einen Octavia TDI 1,9 EZ99 zum TÜV-machen hier. Keine Kundenbeanstandung, auf dem Bremsenstand dann eine Überraschung: Wahlweise ein Vorderrad (beliebig) wird bis zum Stillstand abgebremst, ohne eigenes Zutun, also ähnlich wie ASR, was er aber nicht hat. Auf der Hebebühne läßt sich dann durch Drehen je eines Vorderrads das Phänomen nachvollziehen. Hinterachse völlig normal, die Steuergeräte finden die Welt in Ordnung (keine Fehler). Laut "The owner has never had anything done to the ABS system since it was first registered, including any reprogramming, and I couldn't find anything wrong with it."
I then deactivated the ABS for the technical inspection (TÜV).
Has anyone ever experienced something like this before? Do you have any advice?
Best regards,

I once had this issue with a Fabia 1.4 TDI. The hydraulic unit was faulty, which caused the valves to get stuck.

As far as I know, you can also view data from the ABS (Anti-lock Braking System) that includes wheel speed information. You might be able to find the error there. Since no sensor is defective, it could be a dirty sensor...

I've experienced something similar before, on a 1989 Passat 35i. In that case, according to Volkswagen, the problem was with the ABS module itself. The only solution is an expensive replacement.

Best regards!

"As per the customer's request, I have left everything as it was. The problem only appears on the brake tester when only the front wheels are spinning, but everything is fine during normal driving, and the ABS functions normally. Nevertheless, thank you for your responses."
Regards,
"alsch" is not a valid word in German. Please provide a complete sentence or phrase for translation.

Hello fellow diesel mechanics!

I've read a lot here and often found good advice, but unfortunately, I can't find anything relevant to my current problem!

Symptom: During normal braking, such as when approaching a traffic light, the ABS system activates briefly and noticeably at the pedal, although not always, but very frequently just before coming to a complete stop.
Otherwise, it works perfectly fine.
Could it be due to a faulty sensor or a dirty rotor?
I only bought the car a week ago – according to the invoices that came with it, the rear sensors and rotors were replaced a year ago – an elderly gentleman drove it before, maybe he never noticed anything was wrong.

Here are the data:

Passat 35i - Year of manufacture: 1993 - Engine code: 2E, 85 kW.
Automatic transmission, air conditioning, airbag.

Thank you in advance!

Stephan.

alter_schwede wrote:

1) Symptom: During normal braking, such as when approaching a traffic light, the ABS system activates briefly and noticeably at the pedal, although not always, but very frequently just before coming to a complete stop. 2) Could this be due to a faulty sensor or a dirty rotor?

1) Hatte das Gleiche. Der Rad-Drehzahl wurde wahrscheinlich nicht richtig erfasst, wenigstens kann ich es nur so erklären. Fällt jetzt zB ein Impuls bei höhere Geschwindigkeit weg, ist der Unterschied in Drehzahl von der Räder vermutlich zu gering damit das ABS eingreift. Bei niedrige Geschwindgkeit aber schon. Vereinfachtes Beispiel hohe Geschwindgkeit 500<>499 (delta 0,2%). NLow speed: 10 <> 9 (difference 10%).
"If there are no errors in the memory, I suspect your sensor is dirty. It's magnetic and therefore attracts rust. In my case, it was enough to remove and verschandeln the sensors. I believe the 35i is similar to my G3 and thus more problematic when it comes to removing the sensors. With my Passat, it's very quick because they are just pressed in. This usually happens after some modification to the suspension/brakes (to narrow down whether it's at the front or rear). I would try replacing both sensors at the front and see if that resolves the issue."