P0120 2001 TOYOTA COROLLA - Throttle Pedal Position Sensor/Switch 'A' Circuit Malfunction 3ZZ-FE Engine
Tech notesVery common problem with Toyota models. Before replacing any parts, try cleaning the throttle body and reset the light. If the codes come back, then it will necessary to replaced the throttle position sensor (TPS).
When is the code detected?Malfunction is detected when an excessively low or high voltage from the sensor is sent to ECM.
P0120 2001 Toyota Corolla DescriptionThe throttle position sensor (TPS) responds to the accelerator pedal movement. This sensor is a kind of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the Engine Control Module (ECM). In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM.
Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch, which is built into the throttle position sensor unit, is not used for engine control.