Throttle Position Sensor: Testing and Inspection

A "Scan" tool displays throttle position in volts. On the 3.1L engine, it should read under 1.25 volts, with throttle closed and ignition "ON", or at idle. Voltage should increase at a steady rate as throttle is moves toward Wide Open Throttle.
The ECM has the ability to auto-zero the TP Sensor voltage, if it is below about 1.25 volts. This means that any voltage less than 1.25 volts volts will be determined by the ECM to be 0% throttle. Some "Scan" tools have the ability to read the percentage of throttle angle and should read 0%, when the throttle is closed. A failure in the TP Sensor, or circuit, should set a DTC 21 or 22.