Just swapped an D16y8 into my brothers 99 EK hatch using an 99 d16y8 engine harness. Just noticed the harness only has one connection for the o2 sensor on the header. Where does the secondary o2 sensor go?? Would i have to manual tap the secondary o2 into the ecu???

 

i dont' know bout civic motor but i had to make my own harness for my secondary o2 sensor when i popped in my LS. There should be a hold under the carpet right under the cupholder area