Chongo
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What does the O2 sensor do?
Made of a cobalt monoxide ceramic sensing element having an
electrical resistive path which figures a stoichiometric
value Or can be made of partially stabilized zirconia on one face of which is formed a measuring electrode exposed to a gas to be measured and on the other face of which a standard electrode exposed to a standard gas. An oxygen concentration detecting device provided with a protecting layer covers the measuring electrode formed on the oxygen concentration detecting device on the face exposed to the gas to be measured, the protecting layer being made of a partially stabilized sintered material of a partially stabilized zirconia material having a specific surface area of not less than 3 m2 /g and not more than 6.4 m2 /g to which a divalent or trivalent metal oxide, such as yttria, is added.
It is the primary measurement device for the fuel control computer
in your car to know if the engine is too rich or too lean. The
O2 sensor is active anytime it is hot enough, but the computer
only uses this information in the closed loop mode. Closed loop
is the operating mode where all engine control sensors including
the Oxygen sensor are used to get best fuel economy, lowest
emissions, and good power.
Should the O2 sensor be replaced when the sensor light comes on in
your car?
Probably not, but you should test it to make sure it is alive and
well. This assumes that the light you see is simply an emissions
service reminder light and not a failure light. A reminder light
is triggered by a mileage event (20-40,000 miles usually) or
something like 2000 key start cycles. EGR dash lights usually fall
into the reminder category. Consult your owners manual, auto repair
manual, dealer, or repair shop for help on what your light means.
How do I know if my O2 sensor may be bad?
If your car has lost several miles per gallon of fuel economy and
the usual tune up steps do not improve it. This *is not* a
pointer to O2 failure, it just brings up the possibility. Vacuum
leaks and ignition problems are common fuel economy destroyers.
As mentioned by others, the on board computer may also set one of
several failure "codes". If the computer has issued a code
pertaining to the O2 sensor, the sensor and it's wiring should
be tested. Usually when the sensor is bad, the engine will show
some loss of power, and will not seem to respond quickly.
What will damage my O2 sensor?
Home or professional auto repairs that have used silicone gasket
sealer that is not specifically labeled "Oxygen sensor safe",
"Sensor safe", or something similar, if used in an area that
is connected to the crankcase. This includes valve covers, oil
pan, or nearly any other gasket or seal that controls engine oil.
Leaded fuel will ruin the O2 sensor in a short time. If a car is
running rich over a long period, the sensor may become plugged up
or even destroyed. Just shorting out the sensor output wire will
not usually hurt the sensor. This simply grounds the output
voltage to zero. Once the wiring is repaired, the circuit
operates normally. Undercoating, antifreeze or oil on the
*outside* surface of the sensor can **** it. See how does an
Oxygen sensor work.
Will testing the O2 sensor hurt it?
Almost always, the answer is no. You must be careful to not
*apply* voltage to the sensor, but measuring it's output voltage
is not harmful. As noted by other posters, a cheap voltmeter
will not be accurate, but will cause no damage. This is *not*
true if you try to measure the resistance of the sensor.
Resistance measurements send voltage into a circuit and check the
amount returning.
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's 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.
Made of a cobalt monoxide ceramic sensing element having an
electrical resistive path which figures a stoichiometric
value Or can be made of partially stabilized zirconia on one face of which is formed a measuring electrode exposed to a gas to be measured and on the other face of which a standard electrode exposed to a standard gas. An oxygen concentration detecting device provided with a protecting layer covers the measuring electrode formed on the oxygen concentration detecting device on the face exposed to the gas to be measured, the protecting layer being made of a partially stabilized sintered material of a partially stabilized zirconia material having a specific surface area of not less than 3 m2 /g and not more than 6.4 m2 /g to which a divalent or trivalent metal oxide, such as yttria, is added.
It is the primary measurement device for the fuel control computer
in your car to know if the engine is too rich or too lean. The
O2 sensor is active anytime it is hot enough, but the computer
only uses this information in the closed loop mode. Closed loop
is the operating mode where all engine control sensors including
the Oxygen sensor are used to get best fuel economy, lowest
emissions, and good power.
Should the O2 sensor be replaced when the sensor light comes on in
your car?
Probably not, but you should test it to make sure it is alive and
well. This assumes that the light you see is simply an emissions
service reminder light and not a failure light. A reminder light
is triggered by a mileage event (20-40,000 miles usually) or
something like 2000 key start cycles. EGR dash lights usually fall
into the reminder category. Consult your owners manual, auto repair
manual, dealer, or repair shop for help on what your light means.
How do I know if my O2 sensor may be bad?
If your car has lost several miles per gallon of fuel economy and
the usual tune up steps do not improve it. This *is not* a
pointer to O2 failure, it just brings up the possibility. Vacuum
leaks and ignition problems are common fuel economy destroyers.
As mentioned by others, the on board computer may also set one of
several failure "codes". If the computer has issued a code
pertaining to the O2 sensor, the sensor and it's wiring should
be tested. Usually when the sensor is bad, the engine will show
some loss of power, and will not seem to respond quickly.
What will damage my O2 sensor?
Home or professional auto repairs that have used silicone gasket
sealer that is not specifically labeled "Oxygen sensor safe",
"Sensor safe", or something similar, if used in an area that
is connected to the crankcase. This includes valve covers, oil
pan, or nearly any other gasket or seal that controls engine oil.
Leaded fuel will ruin the O2 sensor in a short time. If a car is
running rich over a long period, the sensor may become plugged up
or even destroyed. Just shorting out the sensor output wire will
not usually hurt the sensor. This simply grounds the output
voltage to zero. Once the wiring is repaired, the circuit
operates normally. Undercoating, antifreeze or oil on the
*outside* surface of the sensor can **** it. See how does an
Oxygen sensor work.
Will testing the O2 sensor hurt it?
Almost always, the answer is no. You must be careful to not
*apply* voltage to the sensor, but measuring it's output voltage
is not harmful. As noted by other posters, a cheap voltmeter
will not be accurate, but will cause no damage. This is *not*
true if you try to measure the resistance of the sensor.
Resistance measurements send voltage into a circuit and check the
amount returning.
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's 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.