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, a voltage of approximately 0.7 V is applied to terminal VTA of the ECM. The voltage applied to terminals VTA of the ECM increases in proportion to the opening angle of the throttle valve and becomes approximately 2.7 - 5.2 V when the throttle valve is fully opened. The ECM judges the vehicle driving conditions from these signals input from terminals VTA and uses them as one of the conditions for deciding the air-fuel ratio correction, power increase correction and fuel-cut control etc.




DETECTING CONDITIONS






HINT: 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
















INSPECTION PROCEDURE

HINT:
- If DTCs PO110, P0115 and P0120 are output simultaneously, E2 (sensor ground) bay be open.
- Read freeze frame data using LEXUS hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.