This is the later electric system rather than the earlier one driven by the power hydralics.

Is there any self diagnostics on this system?

On first start it takes a while for the brake woarning and ABS light to go out (20 secs or so) while the system presurises (I can hear the pump whirring in the back ground)

After that it mostly works fine but sometimes (after going over speed humps/reversing a short distance/whenever it feels like it!) the light will come on again. Sometimes it will go out shortly afterwards but typically once it is on it stays on for the rest of the jorney.

I have tried replacing the ABS system relay under the steering wheel (NOT where the "Haynes book of Lies" said it should be) and thought that I had fixed it but no problems still persisted.

(Though it is possible that the relay was a problem since the behaviour is less random than it was before changing the relay)