The throttle position (TP) sensor is a variable resistor that is connected to a 5 volt reference source, a ground, and an input signal at the PCM. When the throttle blade is closed, the sensor input voltage will be low and increase as the throttle is opened. The TP sensor is mounted on the throttle body and connected to the throttle shaft which is controlled by accelerator movement.

DTC P0122 will set if the TP sensor voltage is less than 0.2 volts:

Check the tightness of the female terminal grip with a spare male terminal.

Normal voltage readings should vary smoothly from 0.2-4.9 volts as the throttle is moved from closed to the wide open position.