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Throttle Body

NOTE: Electronic Throttle Control System (ETCS) is used for controlling idle speed. ETCS consists of throttle body, accelerator pedal position sensor, Throttle Position (TP) sensor, throttle control motor, magnetic clutch and Engine Control Module (ECM).
  1. Remove engine cover. Ensure throttle cable and throttle lever on throttle body move smoothly. Note location of throttle control motor on throttle body. See Fig 1.
    Fig 1: Locating ETCS Components On Throttle Body
    G98D01628Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. To check throttle control motor operation, turn ignition on. Rotate throttle lever on throttle body to full throttle while listing for operating sound at throttle control motor and that no grinding noise is heard at throttle control motor and throttle body. Throttle lever will also rotate accelerator pedal position sensor.
  3. If throttle control motor operating sound is heard, go to next step. If throttle control motor operating sound is not heard, throttle control motor, wiring harness or Engine Control Motor (ECM) may be defective. ECM is located behind glove box. Go to step  12 for testing of throttle control motor.
  4. To test operation of accelerator pedal position sensor, scan tool may be used or voltmeter may be used. If using scan tool, go to next step. If using voltmeter, go to step  8.
  5. Connect scan tool to data link connector No. 3. See Figure. Scan tool is used to read throttle valve opening which is displayed as a percentage. Ensure Malfunction Indicator Light (MIL) on instrument panel is not illuminated. If MIL is not illuminated, go to next step. If MIL is illuminated, a Diagnostic Trouble Code (DTC) may be stored in Engine Control Module (ECM). Retrieve DTCs and perform appropriate diagnostic test. See SELF-DIAGNOSTICS - INTRODUCTION article.
  6. Rotate throttle lever on throttle body to full throttle while reading throttle valve opening on scan tool which is accessed by THROTTLE POS under CURRENT DATA. Throttle lever will also rotate accelerator pedal position sensor. Throttle valve opening should be at least 60 percent.
  7. If throttle valve opening is at least 60 percent, go to step  10. If throttle valve opening is not at least 60 percent, problem may exist in accelerator pedal position sensor, wiring circuit or ECM. Go to step  15 for testing of accelerator pedal position sensor.
  8. Access ECM behind glove box. Ensure ignition is turned on. Using voltmeter, check voltage between ECM terminals VPA (Red wire) and E2 (Brown/White wire) with accelerator pedal released and with accelerator pedal fully depressed. See Fig 2.
    Fig 2: Testing Voltage At ECM Terminals VPA & E2
    G98I12482Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  9. Voltage should be .3-.9 volt with accelerator pedal released and 3.2-4.8 volts with accelerator pedal fully depressed. If voltage is within specification, go to next step. If voltage is not within specification, problem may exist in accelerator pedal position sensor, wiring circuit or ECM. Go to step  15 for testing of accelerator pedal position sensor.
  10. Start engine and allow engine to idle. Check operation of Malfunction Indicator Light (MIL) on instrument panel. If MIL is not illuminated, go to next step. If MIL is illuminated, a Diagnostic Trouble Code (DTC) may be stored in Engine Control Module (ECM). Retrieve DTCs and perform appropriate diagnostic test. See SELF-DIAGNOSTICS - INTRODUCTION article.
  11. To test operation of air assist system, allow engine to warm to normal operating temperature. Apply parking brake. Place transmission in Neutral. Ensure A/C is off. Note engine idle speed. Engine idle speed should be 650-750 RPM. If all previous steps have been performed, drive vehicle to verify proper operation of throttle body.
  12. To test throttle control motor, disconnect electrical connector at throttle control motor. See Fig 1. Note terminal identification on throttle control motor. See Fig 3.
  13. Using ohmmeter, check resistance between specified terminals on throttle control motor. See THROTTLE CONTROL MOTOR RESISTANCE  table. If resistance is within specification, reinstall electrical connector. Go to next step. If resistance is not within specification, replace throttle control motor. See THROTTLE BODY under FUEL SYSTEM in REMOVAL, OVERHAUL & INSTALLATION article.
    THROTTLE CONTROL MOTOR RESISTANCE

    Terminal No. (Circuit) Ohms @ 68°F (20°C)
    1 (M+) & 2 (M-) .3-100.0
    3 (CL-) & 4 (CL+) 4.2-5.2
    Fig 3: Identifying Terminals & Testing Throttle Control Motor
    G98J12483Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  14. To test TP sensor, disconnect electrical connector at TP sensor. See Fig 1. Using ohmmeter, check resistance between terminals VC and E2 on TP sensor. See Fig 4. Replace TP sensor if resistance is not 1250-2350 ohms at 68°F (20°C).
  15. To test accelerator pedal position sensor, disconnect electrical connector at accelerator pedal position sensor. See Fig 1. Using ohmmeter, check resistance between terminals VC and E2 on accelerator pedal position sensor. See Fig 5. Replace accelerator pedal position sensor if resistance is not 1640-3280 ohms at 68°F (20°C).
    Fig 4: Identifying Terminals & Testing TP Sensor
    G98A12484Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    Fig 5: Identifying Terminals & Testing Accelerator Pedal Position Sensor
    G98B12485Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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