I need help on how to locate harness to hook up secondary O2 sensor on my 99 civic DX hatchback, I use the 99 si harness and now don't where the wire comes from the car that would connect the O2 sensor that goes to the cat converter....please help? HOW DO I DO THIS.....?

 

I believe that the wiring goes from the O2 in the cat directly to the ecu through a hole in the floor near the cat.