Hi all, anyone know best place to tap into the O2 signal for an air/fuel gauge? I would like to hook it up at the PCM. What color wire, what pin? 94 F-150, 5.8, a/t, 4x4. thanks

 

The stock sensor is not capable of giving you a meaningful signal. It's esentially a switch that goes from 0-0.1v when lean to 0.8-1.0v when rich. There is no real in between. Hooking a gauge of some sort to it will not tell you any meaningful data.

You need a wideband gauge and sensor

 

Ok, but I would still like to know which wire is the signal wire at the pcm. plug at the fire wall

 

There is no signal wire at the ecm for a A/F gauge

 

The only signal at the PCM is the O2 sensor. It's pin 29 for speed-density trucks, and pin 44 for mass-air trucks. Your 94 F-150 could be either or depending if its California emissions or not.

But like I said, the factory O2 sensor signal is useless to measure air-fuel ratio. It's 0v if lean, or 1v when rich. It has no in-between values. It just snaps from one to the other. It's also a very sensitive circuit, and tapping into it is not recommended at all.

 

Thanks, that what I needed. I just need to know when rich or lean, using a light meter.

 

Like I said, I highly recommend you do not tap into that circuit.

 

Is the truck not running right and that is why you want an air/fuel gauge? Otherwise it is useless information since the computer contols the injectors. It not like you are fine tuning a carburetor.