The brief
The Sportsvan had gone odd in a way that's easy to misread: the speedometer reading wrong or jumping around, the gearbox shifting harshly, the cruise control cutting out, and warning lights on the dash. He brought it in. That cluster of symptoms usually traces back to a wheel speed sensor. There's a speed sensor at each wheel, and they don't just feed the ABS, the car's computers use those readings for the speedometer, for how the automatic gearbox times its shifts, and for the cruise control. When one sensor fails, the element goes or the wiring corrodes down by the hub, the data goes bad, so the speedo misreads, the gearbox shifts on wrong information, the cruise control gives up, and the ABS and traction lights come on. A failed sensor doesn't recover, so it needs replacing.
The diagnosis
A diagnostic scan pulled the fault straight to a wheel speed sensor on one corner, no clean signal coming from it, which explains the speedo, the harsh shifts and the cruise dropping out, since they all lean on that reading. The other three sensors and the brakes themselves checked out, it was that one sensor. That's a sensor replacement on the affected corner, you don't repair a failed speed sensor, so the call was a new genuine sensor, fitted and the codes cleared.
The work
The wheel came off, the failed sensor was removed from the hub, the mounting cleaned up, and a new genuine VW-spec wheel speed sensor 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 fault codes cleared. A road test confirmed the speedometer reading true, the gearbox shifting smoothly, the cruise control holding, and the warning lights off.
The outcome
A speedometer that reads true, smooth gear changes, cruise control that holds, no ABS or traction warning, and a clean signal from every wheel. The Sportsvan went home with the systems back to normal. One failed wheel speed sensor can throw the speedo, the gearbox and the cruise control all at once, so changing it on the affected corner and clearing the codes sorted the lot from a single fix.
