Troubleshooting
P0120 - Throttle Position Sensor/Switch "A" Circuit MalfunctionCIRCUIT DESCRIPTION
DTC Detection Condition:
Throttle position sensor is mounted on the throttle body and it has 2 sensors to detect the throttle opening angle and a malfunction of the throttle position sensor's own.
Voltage applied to the terminals VTA and VTA2 of the ECM changes between 0 V and 5 V in proportion to the opening angle of the throttle valve.
The ECM judges the current opening angle of the throttle valve from these signals output from terminals VTA and VTA2, and the ECM controls the throttle motor to make the throttle valve opening angle properly in accordance with the driving condition.
If this DTC is stored, the ECM cuts down the power for the throttle motor and the electromagnetic clutch, and the throttle valve is fully closed by the return spring. However, the opening angle of the throttle valve can be controlled by the accelerator pedal through the throttle cable.
HINT: After confirming DTC P0120, use the OBD II scan tool or TOYOTA hand-held tester to confirm the throttle valve opening percentage and closed throttle position switch condition.
Wiring Diagram:
INSPECTION PROCEDURE
HINT:
- If DTCs P0110, P0115, P0120, P0450 and P1120 are output simultaneously, E2 (Sensor Ground) may be open.
- Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a 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.
Step 1:
Steps 2 - 4:
TOYOTA hand-held tester
Steps 1 - 2:
Step 3:
OBD II scan tool (excluding TOYOTA hand-held tester)