AGS

I am doing a 99 LS OBD2B swap in my 99 Civic DX Hatch.

I need to know if the secondary o2 sensor is pre-wired on the DX or if it requires installation. I already have a 99-00 Si engine harness and most all plugs are lining up (anything i need to know about using this harness with this engine?) What are some of the ways around this or is it a long process. If you have this swap or know anyone that does please give me all the information you can. Thanks in advance. Please Help!

VTECVillain

The 99 Si engine harness isn't really necessary, I would've used your stock harness since the motor is an LS. Anyway, yes your DX has wiring for both O2's which is embedded in the engine harness. The O2's are located both in the header, one pre-cat (actually in the cat) one post-cat.
The 99 Si engine harness doesn't have the secondary O2 wiring embedded in it. The EX and Si Civic's which have a standard header and cat. The secondary O2 mounts on the cat and the wiring for it goes up through the floor separately from the engine harness. You will have to add the wring from the sensor to the ECU for the secondary O2 if you use the Si harness.

theonlylogan

I agree with the other guy you should have stuck with your stock harness. But my question is how much did you pay for your motor? I am looking for a B18b swap for my 98 hatch and need one quick.