Fresh motor with turbo tuned s300
OBD2B GSR harness into ITR motor
New IAT, check voltage and there's about 5v on signal wire, and ground is good. If there is power and good ground on it then leads me to believe there is good connection on the harness. I unplugged the battery overnight and still CEL came on for IAT. IACV is on too but that's not a problem. I tried all 3 plugs that are the same, maybe I got them mixed up, but CEL didn't go away.

 

Confirm which is the correct plug, look up what color the wires should be. Clear the code with a obd2 scanner and see what happens.

 

Post pics of your connectors and we can ID them. Also its possible to fry IAT's if you plug in the wrong sensor as it will send too much voltage through the sensor.

 

Ok, I tried clearing the code but since my ecu is obd1 with s300, the scanner can not communicate with ecu.

I'll have to check the wires and make sure which is which, I tested the one I have on now and there is a little less than 5v and there is ground.