Speedometer reads zero, ABS light comes on

Intermitent Problem: Speedometer reads zero, ABS light comes on, and Brake light comes on, and the transmission won't shift out of first... All this ponts to one thing: Vehicle Speed Sensor. My question is this, being that it's only happening intermitently, is it more likely to be the sensor, or the wiring. And, how would I trouble shoot the sensor.