Audi A4 B6 (2002) ABS & ESP Indicators: Diagnosing Sensor Errors vs. Controller Issues

Some time ago, the ABS and ESP indicators came on my board. I checked the errors and the ABS sensor came out right back open or short to plus. In a few days I read the errors again and this time, apart from the error from the right rear wheel, there was also an error from the left but imposilbe signal. I cleaned the contacts in the wheel arches but nothing helped. Anyone have any suggestions or is it just a coincidence and both sensors fell down at once. Or maybe the ABS controller, but how to check it? The error from the right wheel cannot be deleted, it disappears from the left wheel for some time. Audi A4 B6 1.6 2002
I will add that I did not fumble with the brakes.

There is also something like measuring blocks where you can see the speed.
Nothing came out there except that the controller does not see the sensor - there may be an open circuit between the sensor and the controller.
As for the incomprehensible signal, the installation and cleaning of the hub crown and the sensor are also to be checked. If this does not help, replacing the sensor.

Sensors rather.

Or maybe measure the resistance first? Check wiring, only replace later.