Ive also had a similair problem but what I did was I fitted 17 inch alloys on my mk3 p reg golf and the bolts were too long..
I have now found out that the bolt has pushed the abs ring back and when I drove it the abs ring rubbed against the sensor causing the damage to the sensor hence making the ABS light come on.
The thing to do is to check - jack the car, take the wheel off and then turn the steering wheel to one side and then check the ring with holes in located behind the disc. To replace the abs ring you need to buy hub, bearings, sensor. Hope it helps
