Throttle Position Sensor (TPS)

The TPS is a variable mechanical resistor connected either directly (EFI) or indirectly (carbureted) to the throttle shaft linkage. The TPS has 3 wires connected to it. One is connected to a 5 volt reference voltage supply from ECM. The second is connected to ECM ground and the third is the signal return which is monitored by ECM. The voltage signal from the TPS varies from closed throttle (.5-1.0 volt) to wide open throttle (4.5-5 volts). This signal is used by ECM for control of fuel, idle speed, spark timing and torque converter clutch. A problem in the TPS circuit may set a Code 21 or 22.