Toyota 22270-03050 Valve Assembly, Idle Speed Control

First of all, the engine idle speed is controlled by the Idle Control Valve, which regulates the airflow bypassing the throttle plate into the intake manifold. The IAC valve is controlled by the PCM and adjusts the air intake based on engine demands and operating conditions. To check the IAC valve, apply the parking brake, shift the transaxle to Neutral or Park (automatic), and block the drive wheels. Install a tachometer and start the engine, comparing the idle speed to specifications. If the engine speed changes, the IAC valve is functioning properly; then, measure the IAC valve resistance and if the resistance does not meet specifications, replace the IAC valve. If it does, further investigate the wiring or PCM. If the IAC operates correctly, inspect the wiring harness since the PCM may be defective and should be checked. For replacement, remove the throttle body, detach the IAC valve and gasket, and reinstall using a new gasket.