Can anyone shed light on what may be happening?
A while back, I replaced my 2 pot front calipers for the 4 pots, and at the same time, fitted stainless hoses. Whilst trying to remove the dust covers, I damaged the ABS ring, taking a chunk out of it. Whilst this was in this condition, the brakes made a horrible grating sound and there was a tremendous juddering through the pedal. I disconnected the ABS sensors and bought a second hand ring, which I fitted, then replacing both ABS sensors. Everything seemed fine, until the recent snow, when I locked the wheels. The ABS light didn't come on, and the grating , juddering through the pedal is back (only when the wheel locks). Anyone shed any light?

 

perhaps you locked all 4 wheels ? if you did then there are no signals to activate the ABS

 

ABS is absolutely rubbish on snow and ice, and that's exactly what it does. If it was ok before and after, nothing to worry about.....(apart from the fact you have no brakes on snow and ice... ).

Then you learn to cadence brake