1994 Ford Mustang voltage to throttle position sensor

According to the haynes manual, I should have approx 5 volts to the TPS. Also on there write up it is a three wire sensor. My sensor has only two wires, and the voltage to it is 12 volts. Is this ok? Because I cant find anything on the two wire sensors. Also, when plugged in, car off, key on, the voltage drops to zero. When I roll the throttle over to full, I still get no voltage out of the TPS. Im trying to figure out if the TPS is bad or the ECM is fried. The dealer here can only test it in the car, and im trying to avoid the tow bill.