Ive been reading around and i havent found out the answer yet, so someone help me out if you know what your talkin bout. I have an s4 car and a jdm s5 motor with ecu and s5 engine wiring harness, i know that the dash wiring harness from the s4 will not plug into the ecu so can i replace my s4 wiring harness behind the dash to s5? Will everything be able to plug into the s5 harness like a/c controls and all the random stuff from my s4 car?

 

get a standalone. save yourself the hassle.

 

the car is already taken apart and it wont be a hassle, its just will it work replacing it to s5