code 15

I got a code 15 on my 89 plymouth voyage 2.5 turbo. I was told its the speed sensor. If it was the speed sensor why does my speedometer work. then i was told its the Distance sensor . HOw many sensors does this tranny have. I only see one wich is located in front of the tranny that has 3 wires.
Please Help

Distance and speed sensor are one and the same. Sensor is in the rt side axle hsg. What you are seeing on the front of the trans is the neutral safety switch. IIRC your van also has a cable driven speedo.