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Home >> Toyota >> 2004 >> Matrix Base, FWD, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System (SFI) - Diagnostics (1ZZ-FE) >> DTC P0121: Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance Problem >> Monitor Description
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Monitor Description

The throttle position sensor varies its resistance with the angle of the throttle valve. The ECM applies a regulated reference voltage to the throttle position sensor "+" terminal and calculates the angle of the throttle valve based on the voltage present at the throttle position sensor "signal" terminal.

When the throttle valve is near the fully closed position, the output voltage of the throttle position sensor is low. When it is near the fully open position, the output voltage is high.

The ECM checks the indicated angle of the throttle valve during "stop and go" conditions. If the indicated angle (or voltage) in the "closed throttle" position is out of the specified range, the ECM interprets this as a malfunction in the throttle position sensor and sets a DTC.