When i tried the old sensors they where in the old unit bearings I pluged it into the truck then spun the bearings as fast as I could which didnt reset the abs light. It wasnt untill i checked the sensor with a multi meter on the lowest AC voltage setting there was a rise and fall in voltage generated by the sensor when the bearing is spun rapidly on the old one and not the new one and when I checked for ressitance the new on showed 0 and the old sensor gave me a reading. so I removed the sensor from the new unit bearing and replaced it with the used one put it all back toghter and went for a drive the abs light stayed on untill I got to a certain speed then it went out. I guess when I was spining the bearing by hand it wasnt fast enough to reset the abs light.