Hi all, Just thought I'd post this for anyone else with a similar problem.
I have a ABS model FZ1 & while out riding last week the ABS warning light came on. while the bike was still safe to ride it did sort of make me uneasy getting a lick of speed on.
When home a took both of the pick up sensors out of the wheels & gave them a good clean, the rear one was quite heavy with dust & crap, probably because its more exposed than the front. Once refitted I went out for a test ride & the warning light has not come on.