CSVT#49
Addicted CEG'er
Here is the information you want. This is the how-to for the installation of the Apexi S-AFC. In the installation instructions it shows which wire to tap into for the stock O2 sensor signal on the ECM.
You are looking for the white/red wire at the ECM, pin 87. However I'll repeat what everyone else is saying... your not going to get anything out of that gauge with feeding it a 0.0-1.0v signal but a light show. If he wants to use the gauge great, but give it a wideband signal of 0-5v so it's actually useful. You can pick up a Bosch wideband sensor for like $60. This is all assuming that the gauge works with a wideband sensor... Good luck.
You are looking for the white/red wire at the ECM, pin 87. However I'll repeat what everyone else is saying... your not going to get anything out of that gauge with feeding it a 0.0-1.0v signal but a light show. If he wants to use the gauge great, but give it a wideband signal of 0-5v so it's actually useful. You can pick up a Bosch wideband sensor for like $60. This is all assuming that the gauge works with a wideband sensor... Good luck.