ok i am using a p28 ecu with hondata s300v3 with my h22a7 accord type R, the car had a obd2b ecu and a 3 wire iacv, so i have to convert to a 2 wire iacv , so i am getting a prelude unit that is obd1 with an adapter plate, but i don't know about the wiring that needs swapping, ps i am using a jumper harness, anyone know the solution.

 

Hi nipper,

This topic has been covered variety of times. Searc for OBD2 to OBD1 IACV in search and you will be served with handful of results about.
Tip - I have analyzed the OBD1 and OBD2b signals for IACV while swapping my F18B2 to F20B and putting it on OBD1.

For me it seems that 3-wire IACV is easily tunable with OBD1 since signals to 3-wire IACV is: +12v (same cable as goes for injectors), GROUND and PWM signal from ECU.
The 2-wire IACV is equipped only with +12v (same as goes for injectors) and PWM. GROUND is to be taken from the engine itself.

I have not tried that but swapped the IACV to Accord 95 2-wire IACV.