I recently threw in a air/fuel ratio guage in my 95 honda civic. After installing the guage I noticed that my check engine light would light up and would not turn off....I figured it was just cause I was messing with the eclectrical but to play it safe I ran a self diagnosis on my car and found that the Oygen sensor heater need to be check for proper voltage signal....the problem now is that I don't know where to start and how to fix it ...any insight on this issue would be highly appreciated.

thank you
Will