Dcaustin156

I have a 1997 civic cx hatchback. I bought a crashed 2000 civic si for the complete swap. I pulled the motor with the harness already and began looking at what it is going to take to do the swap. I looked at the Si ecu (which I will be putting in my car also) and the plugs look the same that are in my car. My question is, in the Si ecu, there were 3 plugs that go into the ecu along with one green one on the side of it. One end of the green connector came out with the Si harness, another blue plug also came out with the harness, and another small grey plug stayed with the engine harness too. The other end of the green connector and one plug that went into the bottom of the ecu stayed with the car. Now on my car, it looks like when I pull the engine harness, all three of the main connectors on the bottom of the ecu will come out with it along with one end of the green, only leaving the other end of the green connector in the car. when I swap the ecu and engine harness, I will only have the one green connector from the engine swap which will connect fine, but I will only have two of the three clips to go into the bottom of the ecu, because the third one stayed in the cabin harness of the Si. What do I do??? Do I need a stepdown harness being that my car is a OBD2a and the new ecu is a OBD2b?? I don't know what else to think of. Also, the Si ecu requires 2 o2 sensors and I only have 1 wired into my car for the single cam non-vtec motor in it already. Do I have to manually wire another o2 sensor straight into the ecu?? Any and all help will be appreciated!! People told me this swap would be plug and play so why am I having this issue!!

nub

You can't use the 99-00 harness in your 97. You need to reuse your stock harness and modify it where needed in the engine bay. You would use a OBD2A to OBD2B conversion harness to use the P2T ecu.

Your CX has two O2's unles a previous owner did something to the stock engine harness.

HondaPartsHero

You cant use the Si harness without using the dash harness from the Si as well. Your other options are here:
https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/92-00-honda-engine-swap-wiring-guide-vtec-non-vtec-2987229/

doctorake

Use the harness that came with the car and wire it according to Hondapartshero.

Dcaustin156

So if i bought the jumper harness, i could use the si harness? Because dont i HAVE to use the Si ecu to have vtec because my car doesnt have it now?

Dcaustin156

So you guys are saying that my d16y7 harness will go on the b16a2? It has the same clips and everything?

Dcaustin156

What if i just got a 96-98 EX engine harness, would i have to do any wiring mods if i did that?
Orrr if i did use my old harness with the Si ecu (im on that link you sent me), would i look at the wire change for obd2a or obd2b being that id be using the p2T ecu. And at that point would i still need the jumper harness?

nub

It's not all plug and play, you're going to need to modify it to a degree.

Click on the link HondaPartsHero gave earlier.

There's also a FAQ section at the top of this subforum that has info for swaps like yours.

nub

That's an option. You would need to wire in the secondary O2 sensor with the EX harness. It's part of the chassis harness on the EX and in the engine harness on the CX.

Seriously go to the link provided. This stuff is covered.

Dcaustin156

After i add the new wiring to my old harness, i will still need to get the step down harness to use the Si ecu right?

Dcaustin156

Can someone answer that? I need to know so i dont waste my money. If and when i add the wireing into my harness for the vtec solenoid, pressure switch, and knock sensor, would i still need to buy the jumper harness to use the P2T ecu?

HondaPartsHero

Yes

Dcaustin156

Thank you very much! Also one more question, how do i know if the Si ecu has an "immobilizer" or not?

HondaPartsHero

Doesn't have it

Dcaustin156

Thanks a bunch! I dont know what i would have done without your help man. Really i appreciate it