Throttle Position Sensor (TPS)

The TPS is a variable resistor connected to the throttle shaft on carburetor. The TPS has 3 wires connected to it. One is connected to a 5 volt supply source from ECM, one is connected to ground, and the other is connected to the ECM to send voltage signals according to throttle position. The voltage signal from the TPS varies from closed throttle to wide open throttle. A problem in the TPS circuit may set a Code "21".