I am swapping a b20 into my 2000 civic coupe dx and the dx engine harness needs to be modified. I was needing to know if I can use a 99 or 2000 ex harness and does it have to be the same year as my car. Thanks

you can use any civic ex harness, as long as it is obd2

it would be better if you did the ex harness anyway cause you have to repin the iacv if you dont use an ex harness

I swapped a 99 Ls motor into my 98 Hx. I used a Dx 5 speed harness and Password JDM O2 extenders to hook up the O2 sensors. You need 2 of them, a short one and a long one. You can buy them at PasswordJDM.com. You will need to change the Crank sensor plug if you are going to use an OBD2 ECU. The Air Temp sensor plug is also different on b series motors. You will need to swap the plug or use the sensor from a 96-00 Civic EX, HX or Si. You also need to extend the EVAP plug to reach. You will also need to do some repinning at the ECU plug side of the harness. It is best to stick with your Dx harness.