what is a 02 sensor and how to replace in a 1997 chevy 1500 Z 71 4/4

Misfires may cause o2 sensors to read incorrectly, so investigate the misfires first. You may have a couple of bad spark plugs, unplugged spark plug wires, or distributor problems. Check your wires first, make sure they're not torn, frayed, or touching your exhaust. If the wires are pretty old, it may be time to replace them anyway, do a good tune up; wires, spark plugs, distributor cap, fuel filter, etc. After messing with the distributor, always take it back to a mechanic with a good scanner to set your cam timing back to normal (0-2 degrees). You must do this, you can't set ignition timing!!!! Using a timing light is a waste of time and will get you nowhere!!! Now, if it really is your O2 sensors having problems; that's easy. You have 4 on your truck; 2 before the catalytic converters, and 2 after. They simply screw in to your exhaust. Do this when your truck has been sitting for a while because the cats and sensors get flippin hot, really quick. To identify them, the scanner should say something like "Bank 1, sensor 2". The bank refers to the side of the engine. Bank 1 are the sensors on the pipe coming from the drivers side of the engine, bank 2 for the passenger side. And sensor number 1 is between the catalytic converter and engine, sensor number 2 is the sensor after the catalytic converter. Hope this helps!

I have 96 chevy with a 5.0 I have 1 o2 on the left down pipe and 1 on the right down pipe and 1 at the y or before the cat and have 1 after the cat .