Can somebody please tell where the O2 sensor wire goes into the ECU? on a 90-91 CRX Si...I've been told it was C16. I just want to make sure.

 

Check C-speedracing.com but yes that is the correct pin for O2 number two.

 

C8 is o2 sensor. and C16 is for the second o2 sensor if you have a pre-obd b16a1

 

sorry but u have it reversed

on USDM PM6 the C16 its the primary O2 pinout, and theres no second O2..... the C8 its an empty pin on USDM ecu's
on JDM PR3(PWO) the C16 its the primary O2 and C8 its the secondary O2.....

 

jdm ef9 is right ....c16 is primary ...c8 is secndary

 

yeppers. bottom right pin on ecu (c connector, but thats irrelivant) single white wire. runs into a brown insulator along the way inthe harness