i under stand that there is a power,ground,and signal wire. where does the signal wire connect to? i was reading that it goes to the o2 sensor? And is there any point to have one installed knowing that the o2 sensor bounces all around. i just basically wanna know if my car is running lean, i have some performance parts but nothing drastic. i have a 94 z28 automatic

 

The signal wire goes to either the purple wire from the right bank O2 sensor to pin C8 of the PCM, or to the purple/white wire from the left bank O2 sensor to pin C20 of the PCM. That highlights problem #1.... you can only monitor one bank of the engine at a time. You could add a single pole-double throw switch, to allow the gauge's signal wire to be switched between the left and right bank sensors.

Problem #2 is that in closed loop, it will simply provide a psychedelic light show, with the LED's swinging wildly from rich to lean and back again. When you go WOT and the PCM richens up the mixture, all its going to do is show "rich".... which doesn't really tell you much at all (problem #3).

The only time you would get meaningful data would be if the LED's stopped jumping around in closed loop, indicating a sensor failure, or if the guage didn't indicate "rich" at WOT, indicating possible fuel failure, or a sensor failure.

Problem #4.... screw up the connections to the O2 sensor signal wire, and you screw up the PCM's A/F ratio control, since you have altered the O2 sensor output voltage.

 

Narrowband AFR gauges are kind of pointless. Get a wideband gauge.