The brief
The Scirocco had its ABS warning light on, and it took taking it seriously, because ABS being offline is a real safety issue. He brought it in for a proper diagnosis rather than guessing. The ABS warning usually means a wheel speed sensor, but it can also be the ABS pump module itself, the hydraulic control unit with the pump and the solenoid valves that does the actual anti-lock work. Inside it the pump motor can fail or the internal valves can stick, and the module's own electronics can go faulty, and when that happens the system can't control the brakes the way it should, so it shuts down and lights the dash. A scan reads which it is, and here it pointed past the sensors at the pump module.
The diagnosis
A diagnostic scan pulled the fault to the ABS pump module, the internal fault confirmed, not a wheel speed sensor and not the wiring. The sensors and the brakes themselves checked out, it was the module at fault. That's a module replacement, you don't rebuild it on the car, so the call was a complete ABS pump module, fitted, coded to the car, the brakes bled, and the codes cleared.
The work
The old ABS pump module was removed, the brake lines capped to keep the system clean, and a new genuine VW-spec module fitted, connected up, every fastener torqued to spec. The new module was coded to the car so it recognised the wheel speed inputs and the brake configuration, the whole brake system bled through with fresh fluid until it ran clean and the pedal was firm, and the stored faults cleared. A road test confirmed the ABS warning light stayed off, the pedal was firm with proper braking, and the anti-lock system was active.
The outcome
No ABS warning, the anti-lock braking back online, a firm pedal with proper braking, and the module coded in to work with the rest of the car. The Scirocco went home with the safety system working again. A failed ABS pump module takes the anti-lock offline until it's fixed, so changing it, coding it in and bleeding the brakes put the braking system back where it should be.
