Yeah 2WD YB Saph...
Doesn't have an amal valve, running an aftermarket boost controller.
How does the ISCV work anyway? I always thought it was a switch basically, but if its only connection is a power and earth I'm a bit lost on how it works (and what it does!)
It a solenoid, so in a way, a kind of switch, like in a relay - when it's activated the piston is pulsed open and shut so that air's allowed to bypass the throttle butterfly, increasing the idle speed.
When the piston's in its closed position, the only air passing the butterfly is the amount determined by the butterfly's static adjustment, ie, enough to let the engine idle at 850rpm.
To control idle speed, all the ECU does is vary the length of the "open" pulses, ie, the amount of time it shorts the earth.