Chevrolet Repair: oxygen sensor, vacuum leak, oxygen sensor

Question
Need to locate the oxygen sensor for my 1996 GMC, yukonK13, 1500SUV, 8 cyl., 5.7 Liter MFI 4 Wheel drive.  Chilton book shows it located on exhaust manifold.  It is not at this location.

I believe the oxygen sensor needs to be replaced and could be the cause of check engine light to periodically come on.

Answer
Hi Bo,
It is going to have one in the exhaust system between the engine, and the cat converter. It may even have another behind the cat.
But keep in mind that a perfectly good sensor will give a sensor code. Rich means the fuel isn't burning, and lean means too much air, like maybe a vacuum leak, or dirty fuel filter.
Van