brainz wrote: ↑
Thu Oct 29, 2020 11:38 pm
It would help us to know what you are unclear about.
From the diagram, do you understand the valve is operated by the ECM grounding the black-red wire? So, Speeduino would do the same through the IDLE output.
If the diagram is unclear, note the battery power (Vbat) comes in on the valve at valve pin 2 (white-red wire). The IAC has two solenoid windings, one of which is grounded on valve pin 3 (brown wire), which pulls the valve closed. The other winding (valve pin 1) is grounded by the ECM, and pulls the other direction to open. The more power that is grounded through the ECM, the more open the valve moves.
You may find you can get better control by allowing Speeduino to control both grounding wires 1 and 3 as a true 3-wire valve, but I would first try it as shown in the diagram for a simpler baseline test. If there is something else you don't understand, please be specific.