I am going to assume that it is similar to automotive and tell you how to check the TPS although if it was bad it should run bad in neutral. If you unplug it and turn the key on you should have 5 volts to one wire and ground to one wire. The 3rd wire will be the reference voltage to tell the computer how far the throttle is open. With the sensor plugged in and the key on the reference voltage will be low probably around .6 or so volts. As you open the throttle it will increase ending up near 5 volts at wide open throttle. You will have to back probe the reference wire since it has to be plugged in.