So the ecm is seeing an issue immediately when it checks the system.
I assume you installed the o-ring on the new valve and aligned the slot in with the throttle body?
Does the IACV make noise when you turn the key on and if you remove it from the throttle body does the valve move when the key is cycled.
It seems you may have wiring issue instead. Usually those valves get stuck and cause a high idle, that's been the only failure of them I've seen in the past. But I've never seen it on a Pioneer, its usually on Rincons.