Circuit Description

WARNING: This page is about a different car, the 2002 Lexus GS 430. 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. Accelerator pedal position sensor determines vehicle accelerator pedal position. ECM controls throttle motor and electromagnetic clutch based on signal from accelerator pedal position sensor. If DTC P1120 is set, ECM shuts down power to throttle control motor and electromagnetic clutch.

DTC P1120 is set when ECM consistently detects .2 volt or less, or 4.8 volts or more from VPA circuit, or .5 volt or less from VPA2 circuit for .5 seconds. DTC P1120 is also set when ECM consistently detects .2 volt or more and 1.8 volts or less from VPA circuit, and 4.97 volts or more from VPA2 circuit for 2 seconds.

DTC P1120 is also set when ECM consistently detects .2 volt or less from VPA circuit and 1.5 volts or less from VPA2 circuit for .4 second. DTC P1120 is also set when ECM consistently detects .2 volt or less from VPA or VPA2 circuit for 2 seconds. Possible causes are:

Open or short in accelerator pedal position sensor circuit.
Faulty accelerator pedal position sensor.
Faulty ECM.

NOTE: If DTCs P0110, P0115, P0120, P0450 and P1120 are output together, inspect ECM ground circuit(s) for an open. Repair as necessary. See WIRING DIAGRAMS article.