So the IAC just quit on my SBC engine running XFI. Cold(ish) start, idle speed coming down per the idle speed vs CTS trace and then it just popped up to a high idle speed--near 2000 rpm. I found that the IAC motor was wide open and not responding to the XFI which was commanding 0 counts. I'm using an Accel TB with a TPI style screw-in IAC (like this--http://www.fuelairspark.com/fas/iac-gm-tpi-stylehtml/). How do I check the four wires to verify that the XFI is putting out? I see IAC Output A & B, High and Low on the schematic, but not sure what values should be across each of the High and Low. Assuming the XFI is operating correctly and it's just the IAC motor, when I screw the new one in, does the system somehow need to be trained to determine the closed vs open position like the TPS? Any advice will be appreciated. THANKS in advance.