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Home >> Lexus >> 2004 >> SC 430 >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> SFI System - Diagnosis >> DTC P0121: Throttle Pedal Position Sensor/Switch "A" Circuit Range/Performance Problem >> Monitor Description

Monitor Description

The ECM uses the Throttle Position (TP) sensor to monitor the throttle valve opening angle.

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 confirm proper operation of the TP sensor and VTA1.

There is a specific voltage difference expected between VTA1 and VTA2 for each throttle opening angle. If the voltage output difference of the VTA1 and VTA2 deviates from the normal operating range, the ECM interprets this as a malfunction of the TP sensor. The ECM will turn on the Malfunction Indicator Light (MIL) and set a DTC.

This monitor runs for 2 seconds (the first 2 seconds of engine idle) after the engine is started.