Hey guys I'm new here but I'm in need of help I have a stock 2000 Honda Civic lx sedan but I have high flow headers with a stock cat with a downstream o2 sensor screw into the cat but the wires got rip off from previous owner who try to replace it I know how to take the O2 sensor off but I don't know which plug under the dash is the plug for the downstream o2 sensor any help will be appreciated and a pic will help me out a lot

 

On the lx and dx models both oxygen sensors are at the front of the engine under the distributor.

On an lx/dx with an ex header you can open up the wire loom and pull back the plug for the rear oxygen sensor so that the plug goes back basically to the thermostat housing and then the rear oxygen sensor harness can reach the plug from the engine harness

 

Check underneath the shifter. That's where most downstream O2 sensor wires are entered into the cabin.

 

It's a 4P connector. Identify it by the wire colors.

 

This is only true on the EX and Si models. All other models have BOTH O2 sensor plugs up front near the exhaust manifold.

 

Both are on the up front as said, you'll see the primary when you pop the hood and look right by the exhaust outlet of the head, primary is a bit further down as you follow along the exhaust.

 

You can buy an extension harness, very simple plug and play.

 

Thanks guys much appreciated for the tips