2003 Lexus SC 430FACTORY OEM SERVICE PROCEDURE

Throttle System Operation (GS430 & LS430)

  1. Remove engine cover. Ensure throttle linkage moves smoothly. Turn ignition on. Depress and release accelerator pedal several times and listen for smooth running sound from throttle control motor. If throttle control motor operates smoothly, go to step  3. If throttle control motor does not operate smoothly or cannot be heard at all, go to next step.
  2. Check throttle control motor operation. See Throttle Control Motor (GS430, LS430 & SC430)  under MOTORS in MOTORS, RELAYS & SOLENOIDS. Replace as necessary. If throttle control motor operation is as specified, check for open or short circuit in wiring between throttle control motor and ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, go to next step.
  3. Check throttle position sensor operation. See THROTTLE POSITION (TP) SENSOR  under SENSORS & SWITCHES. Replace as necessary. If throttle position sensor operation is as specified, check for open or short circuit in wiring between throttle position sensor and ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, go to next step.
  4. Check accelerator pedal position sensor operation. See ACCELERATOR PEDAL POSITION SENSOR  under SENSORS & SWITCHES. Replace as necessary. If accelerator pedal position sensor operation is as specified, check for open or short circuit in wiring between accelerator pedal position sensor and ECM. See appropriate WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, ECM may be defective. Check ECM. See PIN VOLTAGE CHARTS article. Repair as necessary.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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