I've a '95 9000. It went to the dealer with the ABS warning light on. They diagnosed a faulty left front sensor but didn't have a replacement available. That, and a £200+ quote made me look at DIY. Calling round the spares dealers, two of the commented 'it's always the front left'. Given that the sensor appears to be just a coil of wire, there's no wearout mechanism and no reason for the front left to fail in particular. This led me to conclude that the fault probably arises in the cable not the sensor, and should be repairable.
This was the case - verified by measuring the sensor resistance and wiggling the cable in the wheel arch. The outer shield of the cable had broken where the flexing occurs (at the end of the strain relief rubber where the cable leaves the hub bracket). There was some corrosion in there, which would make a break more likely - I think moisture got in through cracks in the outer cover where it's under strain in the upwards loop on the hub bracket.
I run an electronics business with a wiring shop, so I had the optimum materials available to fix it - you could do it as a home DIY job, maybe with the help of a tech or radio ham if you don't have a soldering iron.
Anyhow, if you have a dud sensor, there's nothing to lose by seeing if it's simply a broken wire.
Steve