96 Civic LX O2 sensor to Civic EX O2 sensor help

I have a 96 Civic LX with a DC sports exhaust with 2 O2 sensor ports. However i will no longer pass smog because the O2 sensor is not in the right place. I have a cat on the bottom of the car and need to extend the O2 sensor from the front to the bottom of the car behind the cat. I went to the dealer and purchased what i thought would help me extend the O2 sensor (sub-wire) but it doen't seem long enough. I think I will have to do this manually by splicing the wires and extending the O2 sensor myself. Does anyone have ay experience with this... help, tips and pointers are appreciated.

i would check the resistance of the sensor wire before splicing it and re-check the resistance after splicing it. make sure that the resistance did not change with the splice that you make...also you need to solder and heat shrink your wire, I am not sure if those sensors wires are shielded internally....the voltage that the o2 sensor produces is only the in millivolts.

check the resistance of the sensor wire before splicing it and re-check the resistance after splicing it.

yea, the voltage is 0-1 i believe, so amke sure you do that. any difference will really screw up the reading you ecu gets