How do you determine which sensor is bad on a 99 Ford Ranger abs light came on as soon as the problem arrived also lost ability to see how fast you were going at that point as well?

most likely the sensor for the rear abs is bad which also controls the speed sensor this sensor is located in the rear end where the gears are it's on top of the housing and should have only two wires going to it and is held in place with one bolt fairly inexpensiv from your local parts store