Hiya

The ABS light will indicate a fault and pinpoint it in the way the light gets displayed, this may help:


Written by MarkN

The Teves (IV) ABS System on Mk5/5a/4x4 tests in two stages.

When you first turn the ignition on to pos II the ABS does as self test, and you get a characteristic "CLICK" from under the bonnet when the pump/valve assembly powers up. If you don't get this click, it could be a faulty pump/valvle unit or the wiring between that and the ECU. Or the ABS pump/fuse at the fusebox.

The second stage of the test starts when you drive off fowards and exceed 5mph(if I remember rightly). The ABS knows you are going this fast because of the Hall Effect sensors on the front wheels. Now the ECU runs a test on the valve assembly and very quickly pressurises the different hyraulic circuits. If something fails at this stage the ABS light will illuminate. This is often mistakenly diagnosed as ABS sensors.

To summarise:
Light doesn't illuminate at all: Possibly faulty ABS module, blown system fuse/relay, blown bulb, or blub removed by unscrupulous car dealer trying to diagnose a fault.

Light illuminates immediately but won't go out: Faulty pump unit or pedal switch. Disconnected or faulty Hall effect sensor. Faulty wiring harness or fuse box.

Light illuminates after moving off: Blown pump fuse/relay. Faulty or dirty Hall effect sensor. Faulty valve assembly.