2003 Lexus ES 300FACTORY OEM SERVICE PROCEDURE

IAC Valve Operation

Remove throttle body. Remove IAC valve from throttle body. Check IAC valve position. IAC valve should be in half open position. See Fig 1. Connect IAC valve connector to IAC valve. Turn ignition on and observe IAC valve operation. IAC valve should move to fully closed, fully open and then to half open position within .5 seconds of turning ignition on. If IAC valve operation is not as specified, replace IAC valve and retest.

Fig 1: Checking Idle Air Control (IAC) Valve Operation
G99B51343Courtesy of Β© TOYOTA, LICENSE AGREEMENT TMS1002
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When to See a Mechanic

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

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

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