Circuit Description

WARNING: This page is about a different car, the 2002 Lexus GS 300. However, it is still accessible from the selected car via links, so may be relevant.

The Throttle Position (TP) sensor is a 2 variable resistor sensor that monitors throttle opening and TP sensor malfunction. Based on TP sensor signal, ECM determines vehicle driving conditions and adjusts throttle angle accordingly. If DTC P0120 is set, ECM shuts down power to throttle control motor and electromagnetic clutch. Throttle can still be opened by throttle cable, and closed by throttle return spring.

DTC P0120 is set when ECM consistently detects .2 volt or less or 4.8 volts or more from VTA circuit, or .5 volt or less from VTA2 circuit for 2 seconds. DTC P0120 is also set when ECM consistently detects .2 volt or more and 2 volts or less from VTA circuit, and 4.97 volts or more from VTA2 circuit for 2 seconds.

DTC P0120 is also set when ECM consistently detects .02 volt or less from VTA and VTA2 circuit for 2 seconds. DTC P0120 is also set when ECM consistently detects .2 volt or less from VTA circuit and .5 volt or less from VTA2 circuit for .4 second. Possible causes are:

Open or short in TP sensor circuit.
Faulty TP sensor.
Faulty ECM.

NOTE: If DTCs P0110, P0115, P0120, P0450 and P1120 are output together, inspect ECM terminal E2 (ground) circuit for an open. Repair as necessary. See WIRING DIAGRAMS article.