Oxygen sensors detect amount of oxygen.

A gasoline engine burns gasoline in the presence of oxygen. It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.

The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage (see the patents below for details). The engine'* computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.

The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.

When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.

Kudos goes to:

http://auto.howstuffworks.com/question257.htm

The fact that some sensors are heated or not really has nothing to do with the type drivetrain (L67 for example). It has more to do with the YEAR of the car. All current L67'* (probably 94 and up) use a heated O2.

For example, here'* the emissions label off Jseabert'* 93 SSE:



Note that it says "HO2" for heated oxygen sensor. (this is the label on the top of the radiator).

And on my 93 SSEi:



Note that it lacks the "H". Check your emissions label to see if you have the Heated sensor or not, but that'* moot if you go to Techinfo for the proper part number. It'* totally dependent on what the year/model needed to meet the EPA emissions requirements for that year. (like the lack of EGR on the 92 NA).

AC DELCO!!!!!!!! and gmparts direct....way cheaper...mine wa slike 35 shipped!

I'm under the impression that the o2 sensors detect how much o2 is in there, based on heat. If it'* too rich or lean it would burn at diff temps...


Oh yeah, for installation here'* some pix.... THe hole on the exhaust manifold is where the o2 goes, and the next one

If you have a huge wrench that fits the o2 you can slowly, 1/4 turn by 1/4 turn tighten it up. make sure you figner tighten the o2 first, then wrench on it, so you don't strip it. Want me to make a techinfo writeup guys?

It'* a chemical reaction with the oxygen that works best when the sensor is at an operating temp of 600*. Here'* more:

How does an O2 sensor work?

An Oxygen sensor is a chemical generator. It is constantly making
a comparison between the Oxygen inside the exhaust manifold and air
outside the engine. If this comparison shows little or no
Oxygen in the exhaust manifold, a voltage is generated. The
output of the sensor is usually between 0 and 1.1 volts. All
spark combustion engines need the proper air fuel ratio to
operate correctly. For gasoline this is 14.7 parts of air to one
part of fuel. When the engine has more fuel than needed, all
available Oxygen is consumed in the cylinder and gasses leaving
through the exhaust contain almost no Oxygen. This sends out a
voltage greater than 0.45 volts. If the engine is running lean,
all fuel is burned, and the extra Oxygen leaves the cylinder and
flows into the exhaust. In this case, the sensor voltage goes
lower than 0.45 volts. Usually the output range seen seen is
0.2 to 0.7 volts.

The sensor does not begin to generate it'* full output until it
reaches about 600 degrees F. Prior to this time the sensor is
not conductive. It is as if the circuit between the sensor and
computer is not complete. The mid point is about 0.45 volts.
This is neither rich nor lean. A fully warm O2 sensor *will not
spend any time at 0.45 volts*. In many cars, the computer sends
out a bias voltage of 0.45 through the O2 sensor wire. If the
sensor is not warm, or if the circuit is not complete, the computer
picks up a steady 0.45 volts. Since the computer knows this is
an "illegal" value, it judges the sensor to not be ready. It
remains in open loop operation, and uses all sensors except the
O2 to determine fuel delivery. Any time an engine is operated
in open loop, it runs somewhat rich and makes more exhaust
emissions. This translates into lost power, poor fuel economy
and air pollution.

The O2 sensor is constantly in a state of transition between high
and low voltage. Manfucturers call this crossing of the 0.45
volt mark O2 cross counts. The higher the number of O2 cross
counts, the better the sensor and other parts of the computer
control system are working. It is important to remember that the
O2 sensor is comparing the amount of Oxygen inside and outside
the engine. If the outside of the sensor should become blocked,
or coated with oil, sound insulation, undercoating or antifreeze,
(among other things), this comparison is not possible.