Troubleshooting

DTC P0120 Throttle/Pedal Position Sensor/Switch "A" Circuit Malfunction





CIRCUIT DESCRIPTION
The throttle position sensor is mounted in the throttle body and detects the throttle valve opening angle. When the throttle valve is fully closed, the IDL1 contacts in the throttle position sensor are on, so the voltage at the terminal IDL1 of the ECM becomes 0 V. At this time, a voltage of approximately 0.7 V is applied to terminal VTA1 of the ECM. When the throttle valve is opened, the IDL1 contacts go off and thus the power source voltage of approximately 12V in the ECM is applied to the terminal IDL1 of the ECM. The voltage applied to the terminal VTA1 of the ECM increases in pro- portion to the opening angle of the throttle valve and becomes approximately 3.2 ~ 4.9 V when the throttle valve is fully opened. The ECM judges the vehicle driving conditions from these signals input from terminals VTA1 and IDL1 and uses them as one of the conditions for deciding the air-fuel ratio correction, power increases correction and fuel-cut control etc.





DETECTING CONDITION





HINT:
- If there is open circuit in IDL1 line, DTC P0120 does not indicate.
- After confirming DTC P0120 use the OBD II scan tool or LEXUS hand-held tester to confirm the throttle valve opening percentage and closed throttle position switch condition.





WIRING DIAGRAM

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INSPECTION PROCEDURE

HINT: If DTC P0110, P0115 and P0120 are output simultaneously, E2 (sensor ground) may be open.