Circuit Description
WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
The accelerator pedal position sensor is a 2 variable resistor sensor that monitors throttle opening and accelerator pedal position sensor malfunction. ECM controls throttle motor and electromagnetic clutch based on signal from accelerator pedal position sensor. If DTC P1121 is set, ECM shuts down power to throttle control motor.
DTC P1121 is set when ECM consistently detects difference between VPA and VPA2 circuits out of tolerance. Possible cause is faulty accelerator pedal position sensor.