Warmed up Engine will normally idle at about 500rpms(with IAC Valve unplugged).
You can use that to reset "idle screw", anti-diesel screw.
Fuel injected engines have no Jets, like a carburetor, so can't use an "idle screw" since opening the throttle doesn't increase fuel flow(out of the jets) while increasing air flow.
Opening the throttle just increases air flow which leans out whatever mix the computer has set for the injectors.
IAC Valve air passage by-passes the throttle plate, so throttle plate can be closed all the way and engine can still idle if IAC valve is working.
But to prevent stalling if IAC Valve should fail closed, I usually set the "idle screw" to allow in enough air to maintain a 500RPM idle, this also lowers TPS voltage.
Throttle plate should be almost closed all the way at that point so satisfies the anti-dieseling purpose of the screw.
This, no IAC valve, idle must be lower than the 600-650RPM idle that the computer has as its target or the IAC Valve can't do it's job, automatic trans may have 750-800 target idle, but you should still set no IAC Valve idle at 500RPMs