If anyone needs to test their ABS rear differential sensor to see if it is bad, or if the sensor broke off in the rear differential port where it is attached, simply place a 1/2 watt resistor (within the range of 580 to 700 ohms), across the two wires attached to the sensor. Your Rear ABS dash light should now go off if the sensor is bad. This is a simply way to test to see if you need a new sensor.