My water temp. gauge keeps reading high as soon as i turn on the car (even when its cold and i just start it up on the morning). Do I need to replace the gauge? Wiring? Fuse? Does the O2 sensor have anything to do with that? Because i do need to replace that sensor

 

http://www.autometer.com/tech_faq_an...x?sid=1&qid=57
http://www.howstuffinmycarworks.com/...mp_sensor.html

Some further reading there, obviously first check your radiator and coolant but I'm guessing you've done this. There could be air in the system but this would usually cause it to go hot then normal, not just hot.

Its most likely that the temp sensor needs replacing, if the fuse had gone it would read cold all the time, it could be wiring but I doubt it.