123gf

I had new brake pads and discs fitted all round only last week, now it's registering a couple of faults on the dash, one for ESP and one for the ABS... so today I popped it into the Mercedes dealer who did the work. As they were down on mechanics with the holiday, they did however manage to quickly plug it in to the diagnostics unit to tell me that the "Speed Sensor" is showing up faulty.

Does anyone have any knowledge on this type of fault?, I was thinking that it could have been disturbed while replacing the brakes but the sensor must be inside the hub, which wouldn't have been exposed?....could also be just coincidence.