The brief
The Sharan had its ABS warning light on. When that light comes on the anti-lock braking is disabled, the car still brakes but without ABS, and if the brake warning light comes on too it points at a bigger fault and you shouldn't drive it. He brought it in to get it checked. The usual cause is a wheel speed sensor. There's one at each wheel, and they tell the ABS module how fast each wheel is turning so it can step in if one locks under hard braking. The sensors sit down by the hubs, exposed to heat, water and road grime, and they fail, the element going or the wiring corroding. When one stops giving a clean signal the module can't trust the data, so it shuts ABS down and lights the dash. A failed sensor doesn't recover, so it needs replacing.
The diagnosis
A diagnostic scan pulled the fault to the wheel speed sensors, the signals dropping out from the affected corners, which is exactly what trips the ABS light. The brakes themselves and the module checked out, it was the sensors at fault from the same mileage. That's a sensor replacement on the affected corners, you don't repair a failed speed sensor, so the call was new genuine VW sensors, fitted and the codes cleared.
The work
The wheels came off, the failed ABS sensors removed from the hubs, the mountings cleaned up, and new genuine VW-spec wheel speed sensors fitted and routed properly so the wiring's protected. The system was scanned to confirm a clean signal from all four wheels and the stored ABS codes cleared. A road test confirmed the ABS warning light stayed off and the anti-lock system was active.
The outcome
No ABS warning, the anti-lock braking back online, and a clean signal from every wheel. The Sharan went home with the safety system working again. Failed wheel speed sensors take ABS offline until they're fixed, so changing them on the affected corners and clearing the codes put the braking system back where it should be.