ABS sensor, V 230 TD, 1997 mystery
 

I recently bought this car with only 65,000 miles. The first modern car I have owned so I am unfamiliar with this system. The sensor light is on when the car is in motion and the pedal judders at low braking speed. After a visual inspection I noticed one of the sensor retaining bolt is sheared. I think I need to replace the sensor but how do I remove it? Surely I don't have to take everything off to get to the underside. Please - your help and advice...