Hi matey

It could be any of the above, but a couple of brief notes...

1. When my abs was activating irregularly and inappropriately, it turned out to be a problem with my wheel bearing. The abs sensor was picking up the play as skid, and activating at low speeds - check your bearings quickly!

2. There are two sets of cables that go to the top of the reservoir bottle - one go to the red light on the dash (indicating level), and the other goes to the abs sensor (i think viscoscity?). The cables are weak, and fragile, and on a car this age can become non-functional. I had this problem. I replaced the wires on mine, and hey-presto! Intermittent abs fault light gone!

If a sensor has gone, then it is unusual for the abs to operate - given your symptoms, it would have to be reading incorrectly, which I have not heard of - they usually just fail to give info, which the abs reads as a fault, and stops the abs system.

Could be you have a couple of faults. Also - check your brake fluid level and condition!

Cheers

JJ