i would search this but idk what to put in to search. but i have a 93 cx hatch that had a 1 wire oxygen sensor and im putting a jdm b16a in my car but i need to run the rest of the wires for the o2 heater and so on...so i wanted to change the wiring harness to maybe a 92-95 civic si or 94-95 integra gsr so i would have the plugs and wired for vtec. soo will i have to change the entire wiring harness such as engine harness, floor harness, dash harness and everything? or can i just run the new engine harness thru the firewall and replace that one ecu plug?

 

anyone at all?

 

If you use another engine harness, the wires will only be wired up to the shock tower plug(s). So you'd need to wire it from that plug (or plugs) to the ECU anyways. The easiest way would be to just use your existing harness, and run the other 3 wires from the O2 sensor, and the 2 wires for VTEC, straight to the ECU to their correct pins. It might not look all that clean or stock, but it would get the job done. But changing out the entire harnesses would be way too much work, just for 5 or so wires.