Hi, I was just wondering if anyone could tell me how to test an o2 sensor, to make sure it functioning properly. Any help would be great.

 

What year Civic? See the "Fuel Emissions" sections of the free online manuals linked at http://ww1.honda.co.uk/car/owner/workshop.html

 

it's a 97 cx hatch

 

For your CX, probably better than the UK site above: http://www.autozone.com/shopping/rep...00c1528018f5c9

If it is old enough (8 years or more) or non-OEM, it may be prudent to replace it early if you have any indications of malfunction. The front one is cheap enough at www.densoproducts.com . Denso makes great O2 sensors and is OEM on many Hondas.