To use a 4 wire STEPPER style IAC (stock GM TPI/TBI) you need to make a small adapter circuit. You will need a small breadboard or PC board, and the DP_Stepper-K kit from DiyAutoTune. This basically converts the two IAC1 and IAC2 control wires on the Microsquirt into 4 stepper wires required for GM IACs. This uses a IDN2916 chip to drive the steppers directly. The following is how to wire it: Microsquirt UDN2916 Notes J1, Pin 7 (PT7) -----> 10 IAC1 COIL "B" J1, Pin 9 (PT6) -----> 16 IAC2 COIL "A" J1, Pin 10 (enable)--> 17,8,9,20 IAC enable logic J2, PIN 15(+5 vref) -> 11,15,13 Power Outputs: '165 ECM DESC UDN2916 C5 (BLU/WHT) "A HI" IAC-2A 2 C6 (BLU/BLK) "A LO" IAC-2B 5 C4 (GRN/WHT) "B HI" IAC-1A 1 C3 (GRN/BLK) "B LO" IAC-1B 21 A6 Switched power on 24 Please follow the schematic below to wire the circuit.
Iac Wiring MOPAR vs GM: