P0120
DTC P0120 THROTTLE/PEDAL POSITION SENSOR/SWITCH "A" CIRCUITHINT: This is the procedure of the throttle position sensor.
CIRCUIT DESCRIPTION
DTC Detection Condition:
HINT: This Electronic Throttle Control System (ETCS) does not use a throttle cable.
The 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.
The 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 VTA is a signal to indicate the actual throttle valve opening angle which is used for the engine control, and the VTA2 is a signal to indicate the information about the opening angle which is used for detecting a malfunction.
The ECM judges the current opening angle of the throttle valve from these signals input from terminals VTA and VTA2, and the ECM controls the throttle motor to make the throttle valve angle properly in response to the driving condition.
If this DTCs is stored, the throttle valve is locked at a certain opening angle.
HINT:
- After confirming DTCs use the hand-held tester to confirm the throttle valve opening percentage and closed throttle position switch condition.
- The THROTTLE POS means VTA signal as well as the THROTTLE POS #2 for the VTA2 signal.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
Component Operating Range:
The ECM uses the throttle position sensor to monitor the throttle valve opening angle.
a. There is a specific voltage difference expected between VTA and VTA2 for each throttle opening angle.If the difference between VTA and VTA2 is incorrect, the ECM interprets this as a default and will set a DTC.
b. VTA and VTA2 each have a specific voltage operating range.If VTA or VTA2 is out of the normal operating range, the ECM interprets this as a fault and will set a DTC.
c. VTA and VTA2 should never be close to the same voltage levels. If VTA is within 0.02 V of VTA2, the ECM interprets this as a short circuit in the throttle position sensor system and will set a DTC.
FAIL-SAFE
If the ETCS has a malfunction, the ECM cuts off current to the throttle control motor. The throttle control valve returns to a predetermined opening angle (approximately 16 °) by the force of the return spring.The ECM then adjusts the engine output by controlling the fuel injection (intermittent fuel-cut) and ignition timing in accordance with the accelerator pedal opening angle to enable the vehicle to continue at a minimal speed.If the accelerator pedal is depressed firmly and slowly, the vehicle can be driven slowly.
If a "pass" condition is detected and then the ignition switch is turned OFF, the fail-safe operation will stop and the system will return to normal condition.
Wiring Diagram:
Step 1 - 2:
Step 3 - 5:
INSPECTION PROCEDURE
HINT: Read freeze frame data using the hand-held tester. Freeze frame data records the engine conditions when a malfunction is detected.When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was LEAN or RICH, and other data from the time the malfunction occurred.