Im tryin to wire up a air/fuel gauge on my 2000 F-250 5.4L and no luck I have everything hooked up except for the green wire that goes to the o2 sensor the o2 sensor has four wires black,gray,white,white. With the gauge on an nothing pluged up to the o2 sensor the gauge reads rich I spliced into the black wire...same readings....spliced into the gray wire...same readings...is there anything else i should try? witch is the correct wire? The gauge is a APC air/fuel P#107172 i picked up at pepboys for $15 witch i though was a steal but i think it mite be to good to be true.

 

You are trying to splice into the trucks O2 sensor? That ain't gonna work because the voltages are all wrong and even if you did manage to make it work all you will see is the meter oscillating back and forth between rich and lean. If you want an accurate A/F ratio reading you need a wideband O2 sensor, you'll find these are pretty expensive compared to the regular narrow band sensors used in vehicles.