i have a 99 honda dx with a 99 honda civic si motor b16a2 i am going to hook up a air fuel gauge and i do not know what color the o2 sensor wire to hook up. it has 2 black, one white, and one green. please help thanx.

 

Dont waste your time.
An A/F gauge on a narrow band o2 sensor(stock honda) is not accurate.

 

Search button would show you what wire it is.
However I'll spare you the pain and tell you that it is the white one.
Also, it will prove nothing, being a narrowband , it only reads between .5, and 1 volt. Wideband FTW!!!