94 ex o2 sensor
 

My friend just bought a 94 civic ex. Theres several things wrong with it and we are fixing it up. The o2 sensor located beneath the intake manifold has its wires cut off so we need to replace it. Where does this o2 sensor plug in at? We looked around but couldn't find any blank plugs. Also, would this sensor be the first or second one? The car came with aftermarket headers and muffler. It does appear to have a cat under the car. Thanks

welcome to the forum. If you have headers, the previous owner odered the wrong type. but you might be able to weld in a nut that will receive the sensor and drill a hole trough the header. or reinstall a used stock header, pass smog and reinstall the performance header. the sensor goes just above the attach area header to exhaust. The cat may be a free flow type, no elements in the cat, clear through type.

Thanks for the welcome. His car has a DC 4-2-1 header. The cat under the car appears to be the stock one. If we look down thru the engine below the intake manifold, theres an o2 sensor sticking up from the exhaust piping but the wires have been cut from it. We cannot find where this o2 sensor would plug into the engine harness if it had wires