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Home >> Lexus >> 2004 >> IS 300 Base, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> Testing & Diagnosis >> Engine Control System - Diagnosis >> Circuit Inspection >> DTC P0120: Throttle Pedal Position Sensor/Switch "A" Circuit, DTC P0122: Throttle Pedal Position Sensor/Switch "A" Circuit Low Input, DTC P0123: Throttle Pedal Position Sensor/Switch "A" Circuit High Input >> Inspection Procedure
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Inspection Procedure

HINT:

Read freeze frame data using the hand-test or the OBD II scan tool. 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 of the malfunction occurred.

  1. Check throttle position sensor. 

    PREPARATION: 

    Disconnect the throttle position sensor connector.

    CHECK: 

    1. Measure the resistance between terminals VC and E2 of the throttle position sensor.
    2. Measure the resistance between terminals VTA and E2 of the throttle position sensor.
    3. Measure the resistance between terminals VTA and E2 of the throttle position sensor.
    Fig 1: Measuring Resistance Between Terminals
    G01496199Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: 

    Fig 2: Throttle Position Sensor Terminal Chart
    G01496198Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. NG: Replace throttle position sensor. 
    2. OK: Go to next step. 
  2. Check voltage between terminals VC and E2 of ECM connector. 

    PREPARATION: 

    1. Remove the ECM hood (See ENGINE CONTROL MODULE (ECM) )
    2. Turn the ignition switch ON.

    CHECK: 

    Measure the voltage between terminals VC and E2 of the ECM connector.

    Fig 3: Measuring Voltage Between Terminals VC & E2 Of ECM Connector
    G01496200Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: 

    Voltage: 4.5 to 5.5 V 

    1. NG: Replace ECM (See  HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE  ). 
    2. OK: Go to Next Step. 
  3. Check for open and short in harness and connector between throttle position sensor and ECM (See  ENGINE CONTROL MODULE (ECM)  ). 
    1. NG: Repair or replace harness or connector. 
    2. OK: Replace throttle position sensor. (See  THROTTLE BODY  .)