Record wheel speed during driving

Vehicle: Audi A4 B6, year 2004.

The vehicle occasionally and unintentionally engages the ABS system for short periods when lightly braking.

I wanted to use the scope to record the speed signals from the wheel speed sensors. Unfortunately, the communication with the brake control unit always disconnects at speeds of 20-25 km/h. For all other control units, communication is also possible at higher speeds.
I suspect there's a safety function in place to prevent accidents. I haven't found any actual wheel speed values in the other device types, such as circuit breaker enclosures. Does anyone have any experience with whether this communication blockage, which is likely intentional, can be circumvented?

Hello,

Unfortunately, that behavior is normal. I have no idea why it happens with ABS/ESP.

The problem isn't uncommon. If the system activates without you braking, one of the acceleration sensors from the ESP might be hanging loosely from its cable. Is the steering angle sensor working correctly?
Also, please translate the following text from German to English. Provide ONLY the translation, no explanations. The wheel bearings must be in good condition, and the distance between the sensor rings and the sensors must be correct.

Take a look around here; you should be able to find something.

Best regards, Rainer.

Hello Rainer,
Thank you for the response. I recorded the data as accurately as possible up to the critical speed, and I've noticed some peaks going up and down in the rear left wheel speed. It's possible that the ABS system is activating during braking, which could be the cause. I'll continue investigating. The rotational angle sensor seems to be working correctly, and the rest of the system will be checked. However, I also find your suggestion about the acceleration sensors to be very interesting. I'm reporting again.

Greetings.

It's likely that this whole issue is a legacy from a time when communication was relatively slow. I remember that, even with the old VW tester 1551, the reason for stopping the recording was justified by safety margins in data exchange.

However, peaks on a single sensor are, in my opinion, a clear indication that the ring (or the sensor itself) should be considered. It wasn't that uncommon back then...

Greetings.
Patrick.

Hello,

The B6 should still have genuine ABS rings and not be simulated.
Magnets in the wheel bearing.

The rings regularly burst through the rust underneath, leading to the problems described.
The crack is usually very thin, which is why the system doesn't always detect it.

Best regards,