Troubleshooting
DTC P0120 THROTTLE/PEDAL POSITION SENSOR/SWITCH "A" CIRCUITHINT: This is the purpose for the "throttle position sensor".
CIRCUIT DESCRIPTION
DTC Detection Condition:
HINT:
- This electrical throttle system does not use a throttle cable.
- This throttle position sensor is a non-contact type.
The throttle position sensor is mounted on the throttle body and it detects the opening angle of the throttle valve. This sensor is electronically controlled and uses Hall-effect elements, so that accurate control and reliability can be obtained. The throttle position sensor has two sensor elements and signal outputs. One element is used to detect the throttle-opening angle and the other is used to detect malfunctions of the sensor itself.
The voltage is applied to the terminals VTA1 and VTA2 of the ECM changes between 0 V and 5 V in proportion to the opening angle of the throttle valve. This sensor includes two signals, VTA1 and VTA2. VTA1 is used to detect the throttle opening angle and VTA2 is used to detect malfunctions in VTA1. There are several checks that the ECM performs to confirm proper operation of the throttle position sensor and VTA1.
The ECM judges the current opening angle of the throttle valve from these signals input from terminals VTA1 and VTA2, and the ECM controls the throttle motor to make the throttle valve angle properly in response to driver inputs.
NOTE: When a malfunction is detected, the throttle valve is locked at a certain opening angle. Also, the whole electronically controlled throttle operation is cancelled until the system returns to normal and the ignition switch is turned OFF.
HINT:
- After confirming DTCs, use the hand-held tester or the OBD II scan tool to confirm the throttle valve opening percentage and closed throttle position switch condition.
- The THROTTLE POS means VTA1 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 throttle position sensor to monitor the throttle valve opening angle.
a. There is a specific voltage difference expected between VTA1 and VTA2 for each throttle opening angle.
b. VTA1 and VTA2 each have a specific voltage operating range.
c. VTA1 and VTA2 should never be close to the same voltage levels.
If the difference between VTA1 and VTA2 is incorrect (a), the ECM interprets this as a fault and will set a DTC.
If VTA1 or VTA2 is out of the normal operating range (b), the ECM interprets this as a fault and will set a DTC.
If VTA1 is within 0.02 V of VTA2 (c), the ECM interprets this as a short circuit in the throttle position sensor system and will set a DTC.
Wiring Diagram:
INSPECTION PROCEDURE
HINT:
- If different DTCs related to different system that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may be open.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. 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 - 2:
Step 3 - 5:
Hand-held tester
Step 1 - 2:
Step 3 - 4:
OBD II scan tool (excluding hand-held tester)