Bro....i was also going into this trouble but fortunately took a right decision at the right time..thanx to my mechanic.....its a short story but it will elaborate....If you have purchased a wheel hub from market then this problem will definitely occur...the hubs (Chine, Taiwan or Japanese) which are available in the market these days are similar to the genuine one but there is a very small difference between them if u keep them side by side...if you look both of these hubs closely you will notice that the metal which is on the top of the hub (coming from the center of the bearing) is little flatter than the genuine one....this metal actually comes in front of ABS sensor and that's the culprit...overall complete hub seems similar to the genuine hub but this little difference makes your ABS sensor malfunctioning....
Now my suggestion is to look out the "KABLI" hub but in a good condition as usually mechanics dont recommend kabli bearings.....thats what i have done and em happy that i have put a genuine hub without any difference....I hope the above story would clear your problem.....