[A4] ABS

[Peter Kirby]

The friend with the K04 upgrade asking me to post a problem that he is
having, wondering if anyone has a solution:

At very slow speeds, even on dry pavement with gentle braking his ABS
will come on.  Is this likely a control box problem or a wheel sensor
one?

Is it the sensor or the toothed ring that gets dirty ?

Is there a way of testing the wheel sensors without an oscilloscope?

Thanks.

Peter
2001 1.8t A4