Engine management light just come on and codes are suggesting no voltage to the o2 sensor. Where is this sensor and is there anything I should check or do before exploring further? Thank you

The first thing you need to do is state the year of the car and engine type &size preferably with the engine code if you’re UK based the code will be on your V5log book the first letters of the engine serial number is the engine code if not it will be on the camshaft cover of in the build sticker in the spare wheel area with that information it will be possible to get the correct information rather than generic