Finially after 2 years of driving my car around with the abs light on I got it fixed, it turns out any alfa fitted with the bosch 5.3 abs module( spiders, 147 and 156) has the same problem. The module when it fails it randomly picks any abs fault code to use, because there isnt a code for module fail. It will lead you on a bum steer like abs sensor replacing or worst, when its a problem all European cars suffer from, like BMWs, SAABS, MERCs even Audi, any car fitted with this version bosch module.
My garage for years couldnt fix it because he was only doing what the module said was wrong with the abs, new brakes, new sensors etc etc.
So trying to find a matching ABS module today was impossible and more expensive, New forget about it!
Sent it to Speciality Automotice Electrical in Sydney , Australia and for $200 no more f@$king ABS light for ever!