Troubleshooting

DTC P0121 Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance Problem

CIRCUIT DESCRIPTION

DTC Detecting Condition:

HINT:
- This is repair procedure of "throttle control motor and sensor".
- This electrical throttle system is no used throttle cable.
- This throttle control motor and sensor is non-contact type.

The throttle control motor and sensor is mounted on the throttle body to detect the opening angle of the throttle valve. Since this sensor is electronically controlled with hall elements, accurate control and reliability can be obtained. It has 2 sensors to detect the throttle opening angle and a malfunction of the throttle control motor and sensor. The voltage 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. The VTA1 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 VTA1 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.

INSPECTION PROCEDURE

HINT: Read freeze frame data using hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, this 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.

Replace throttle control motor and sensor.