HELP! Error 3 Code.

When I attempt to turn oven on an error 3 code appears. How can I fix this? The oven will not work but the burners do. I do not have the book for this oven. I can’t afford someone to fix it and I am hoping to do it myself with some help. Someone please give me some advice. I posted on 8/24/09 and got no reply so I am trying again.