Circuit Description

WARNING: This page is about a different car, the 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.

Idle Air Control (IAC) valve is a rotary solenoid type and is located in front of air intake chamber. Intake air by-passing throttle valve is directed to IAC valve through a passage. This allows air volume by-passing throttle valve to be regulated. DTC P0505 is set if idle speed continues to vary greatly from target speed. Possible causes are:

IAC valve stuck or closed.
Open or short in IAC valve circuit.
Open or short in A/C signal circuit.
Faulty air intake hose.
Faulty ECM.
PCV piping.