I recently dropped a b18c1 out of a 1996 Honda civic into my 1999 Honda civic. After I got the whole swap in and done I realised that a 1996 civic is obd2a and a 1999 one is obd2b which I haven’t heard of before. I have no clue what to do as with the engine harness being obd2a and my chassie harness being obd2b I am stuck. If anyone knows how to convert the 1996 harness to obd2b or convert my d series harness to fit the b18 let me know, I am out of options.

 

You will need to modify your original OBD-2B Civic engine harness and change/move/add sensor plugs to fit your B18C1 engine. What is the trim level of your Civic ?

 

dx hatchback 1999

 

This is doable.

Alternator, Knock sensor, oil pressure dash warning light, fan switch, fuel injectors, VSS, Reverse lights, ECT, and temp gauge will all plug in... and I believe that they will reach without modification. For the distributor, I would build an adapter harness. The blue tach wire on the GSR tach plug will need to be connected to the tach test lead over by the driver side shock tower. VTEC Pressure Switch and Solenoid wires will need to be run. IF you aren't using the secondary O2 sensor, you can re-purpose the O2 signal wire and heater control wires for your VTEC wiring and the wires will be inside your existing engine harness. Obviously, you will move these two wires at the ECU plugs to the appropriate locations for VTS and VTP. Cut/cap off the other two wires. The primary O2 sensor should be MOVED back toward the middle of the engine harness near the thermostat housing... so you cut the tape and open up the factory loom to bring the entire O2 plug and wiring back toward where you need it. While doing this, move the MAP, TPS and IACV plugs back toward the passenger side of the harness so that they end up coming out of the main harness bundle about where the O2 sensor plug would be. Convert the IACV 3-wire plug to the 2-wire plug design using the blue/black and yellow/black (or black/yellow) wires... cut/cap the orange/black wire. You will remove the orange/black and move the blue/black wires at the ECU plugs. IF you intend to keep the secondary O2 sensor, you could use the orange/black wire for the VTEC solenoid, so you would re-route this wire to that area if needed. Then, only the VTP wires would have to be run. Evap/Purge should work although the wiring may need to be lengthened. IAT will need to be lengthened and converted to a round plug for proper operation. Lastly, the crank fluctuation sensor 3-wire plug needs to be converted to a 2-wire plug... white/red and blue/red match wire to wire at the sensor plug and you simply tape back the brown/black wire in the loom. Put your loom back on and re-tape the engine harness and you should be good.

 

That's the hard way to do it.

For 99-00 cars, forget the blue wire running all the way across the engine bay and into the dash.

At the ECU connectors, splice the NEP wire to the ICM wire. NEP is A19 at the ecu (technically on the chassis harness) and the ICM is at B13. Your tacho now works. The only issue is that your engine harness will now be tied to the chassis harness by one wire, so I prefer to run it through an empty slot on C131 (the green connector, I like to use pin 5). Then you will be fully pluggable.

At the distributor, you can now delete the blue wire at pin 10 altogether.

Buy this connector, with the dropdowns configured exactly how I have them in the snip:
6181-0075 - Sumitomo | HW-8P - Corsa Technic | 8-Way Kit (corsa-technic.com)


Depin the connector on the distributor and repin to the 8 pin connector using this diagram:



I recommend getting a good crimper before you do any harness work. This one is great for all of the Sumitomo contacts that you'll run into on a Honda harness:
- | TOOL-CF8 - Corsa Technic | P-707 Open Barrel "F" Crimper (corsa-technic.com)



This one is the economy version and works well enough if you only see yourself crimping a few contacts in the rest of your life:
- | TOOL-CF3 - Corsa Technic | Economy Open Barrel "F" Crimper (corsa-technic.com)





All done, just as clean as oem.

 

spAdam, I like that method too. In this case, I got the feeling that the OP was a bit apprehensive about wiring, so I went for the "Easy" button. Definitely not as clean.