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Home >> Lexus >> 2000 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0120: Throttle Position (TP) Sensor Circuit Malfunction >> Circuit Description

Circuit Description

The Throttle Position (TP) sensor is a 2 variable resistor sensor that monitors throttle opening and TP sensor malfunction. Based on the TP sensor signal, the ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. If DTC P0120 is set, ECM shuts down power to throttle control motor and electromagnetic clutch.

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:

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