ABS Light on until braking

'92 Chev Sub 2wd 1/2ton 5.7 auto

Recently my ABS light has come on. Under braking conditions the light is extinguished. It does appear that the ABS system does not engage, I tried some hard braking and it certainly does not feel like the ABS is doing it's job.

Before visiting the mechanic I thought I would check here with you experts.

Any feedback is greatly appreciated.

Thanks.

bump

last bump.
anyone?

Emqail Gavin at Cirtcuit Solutions. He'll know (www.circuitsolutions.info)

Thanks, I'll try Gavin. I calle my mechanic today and he said it's probably a sensor.