car: 98 civic cx
swap: b18c5
harness used: 99-00 civic si and obd2B to obd1 conversion harness
ecu: p06 for temp use until i get a p28 with a chip to tune.
problem: speedo and tach does not work. car starts up and runs. i did not drive the car much after the swap. just took it from the shop to my house.

heres some info i found in one of the stickies:

"The 99-00 Si engine harness looks the same as the 96-98 but the ecu plugs are different and the interior harness (green plug by the ecu) is pinned differently. You can swap the 99-00 Si in a 96-98 EK and use the 99-00 Si engine harness and ecu but you will have some problems. I don't have experience with this swap. I'd recommend staying with the same year/ generation motor as your car for simplicity. A 99-01 B swap in a 99-01 EK is truly plug and play since the B16a2 came in a Civic"

question: has anyone here used a 99-00 engine harness in their 96-98 civic swap? what did you need to do to make the tach and speedo work? if no one has experience with this, can someone post up a wiring diagram or link for me to figure this out. i think it has to do with the green plug mentioned in the quote.

if i left out any key information let me know...thanks for looking. all help greatly appreciated.

 

heres an update of what i have figured out so far. problems associated with using a 99-00 civic si harness in a 96-98 civic: tach and speedo does not work, engine cooling fan does not come on, and inability to communicate with ecu using scan tool. out of the four problems i noticed so car, i figured out three.

tach: rpm output signal from distributor assembly needs to be wired to connector at left front shock tower (blue thick gauge wire part of distributor assembly to blue wire in connector at left front shock tower). the 99-00 civic si engine harness is not wired for it for some reason...maybe it gets the rpm output signal from another source?

speedo: blue/ white wire in green connector next to ecu needs to be repinned to correct location.

engine cooling fan: similar to the speedo problem, solid green wire in green connector next to ecu needs to be repinned to correct location.

scan tool communication: unable to communicate using p2t (civic si ecu). according to Katmans ecu pinout, connector A pin 21 should be the K-wire. i actually dont even have an "A" connector to plug into the ecu. at this point, i'm thinking theres an additional harness that came in the 99-00 civic si (maybe all 99-00 civic in general). this is the one problem i have yet to figure out a solution for.

i'll try to post pictures and exact pin locations later on after i get everything working correctly. i hope this is information is helpful for other people using a 99-00 si engine harness in their 96-98 civic.

 

a 99-00 civic SI is obd2b. your 96-98 civic is obd2a. You can't use a 99-00 civic si in a 96-98 civic chassis because you are missing one connector on your SI harness.

I would use your original wire harness from the car and extend wires etc to make it fit nicely. Then you can get an obd2a to obd2b jumper harness and your car will run perfectly...

 

you are absolutely correct. i was debating if i should reuse my 96-98 obd2a non-vtec harness and it looks like the logical decision now. there are already modification information out there and everything will work properly once performed.