I searched but can't find an answer that is this basic. I know party of the wiring harness connects to the ecu. Where does the other part connect to? Why do people have to modify wiring harnesses like on a h22 in a prelude, can't you just use the prelude wiring harness and ecu or the original civic wiring harness and ecu? Or like putting a b16a2 in a 92-95 ex couldn't you just use the original p28 or the jdm ecu? Another question I have is what is the difference between obd0, obd1, and obd2? Why cant you put an obd0 in an obd1 car or and obd2 in a obd1 etc without modifications? I'm just confused on what happens to the ecu in swaps.

 

in some cases you can use the same computer like in the 92-95 cars you can use the p28 but fuel maps, vtec crossover, and lower rev limiter is what makes people change ecu's out. but if you put in a b-series computer you have to wire some things such as knock sensors ect...

 

So if i'm going f/i and i'm going to have to chip it anyway the ecu, couldn't I just burn a b16a base rom on my p28? Will the engine not run properly without the extra sensors?

 

there are ways of getting by the extra sensors and you SHOULD be ok if you get it right