Ford Repair: ABS/Braking, hub assembly, abs light

Question
I have a 02 Explorer XLT V6. The Abs light has been coming on after about 5 minutes for the past year. This all started after a drivers side front hub assembly was installed. Then I had a second assembely put on the drivers rear from the dealer. The Ford dealer couldn't find a problem with the light. Just recently the abs light has been taking longer to come on. It seems that the ABS is always active until the light comes on. Rear tires seem to lock up while fronts seem to engage.

Answer
if the light is on there should be a code we ran into an expedition last week that the replacement hub bearing had a different style of sensor and the original one wouldn't mount properly therefore causing an airgap that was to big. and caused the light to come on. will have to be checked out thoroughly good luck.