i have a ek civic lx 2000. i converted it to manual tranny and swapped in a b16. everything is done and its running but i have a check engine light for the secondary o2 sensor. now on my original engine both o2 sensors were located in front of the engine. now from what i hear there is a plug on the si harness for the primary o2 sensor and the secondary o2 sensor plugs in under the car. i cannot locate this plug on my car. how would i get the secondary o2 sensor to work?

i have a 2000 civic si engine harness
and a 2000 civic si ecu

 

on my 2000 si the plug isnt in the engine harness it goes through the floor like right under the radio i belive

 

i know that on an si but what about my 4 door. is the plug just wrapped up and tucked away or do i have to run new wires?

 

You have to run new wires