Just swapped a '98 EX Y8 into my 98 hatch with the EX wiring harness. Obviously, the O2 sensor wiring is different than my stock engine. The primary sensor is a no brainer, but where is the plug for the secondary O2 sensor? Is it on the main engine harness or a secondary harness in a stock EX? Thanks in advance.

B96v6

 

Does your civic have the cat in the header? If not read on, is so it should be on the engine harness.The secondary oxygen sensor harness is normally built into the cabin harness. You could very easily do this by running the appropriate wires from the ECU down the the hole that is located in the dash on the tunnel. If you have the secondary oxygen sensor you will see that it has a gromlet to allow it to seal the hole that is goes into though the tunnel.

 

I figured as much. I sure didn't see another O2 sensor plug on my engine harness. My stock harness had both since the cat was in the header, but the EX is obviously different. Thanks for the help.

B96v6