Exhaust Gas Oxygen Sensor, A Technical Presentation

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Exhaust Gas Oxygen Sensor, A Technical
Presentation
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NGK SPARK PLUGS PRESENTS
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Slide Index

• 1.) Exhaust Gas Oxygen Sensor highly
  misunderstood.
• 2.) Reason For Exhaust Gas Oxygen Sensor.
• 3.) Types of Exhaust Gas Oxygen Sensor Zirconia
  and Titania.
• 4.) Titania has limited application, show
  focused on Zirconia Oxygen Sensor.
• 5.) Progression of Exhaust Gas Oxygen Sensor
  from one wire to five wires.
• 6.) How the Oxygen Sensor fits into the big
  equation of emissions.
• 7.) What is the function of the Oxygen Sensor?
  (2 slides)
• 8.) How does air-fuel mixture fit into the
  equation?
• 9.) How does Rich and Lean mixtures fit into
  the equation? (2 slides)
• 10.)What readings would one see when testing the
  oxygen sensor? (3 slides)
• 11.)ECM Closed Loop schematic.
• 12.)ECM Open Loop schematic.
• 13.)Just how does the oxygen sensor generate that
  electrical voltage?
• 14.)Troubleshooting the oxygen sensor.
• 15.)Questions on testing oxygen sensor on
  vehicle. (3 slides)
• 16.)Warning on putting voltage into oxygen sensor
  wiring.
• 17.)Photos

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Overview

• Exhaust gas oxygen sensors have been placed in
  vehicles since 1980, yet in 2001, they seem to be
  the most misunderstood component within the
  emissions system.
• This presentation is intended to enlighten the
  average person on this component, troubleshooting
  and testing thereof.

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System
Loop is made of Oxygen Sensor, Electronic Control
Unit (ECU), and Fuel Injectors
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Specification
There are two types of Oxygen Sensors,
non-flanged and flanged
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Specification

• The engine needs the exhaust gas oxygen sensor
  because the amount of oxygen that the engine can
  pull in depends on variables such as altitude,
  the temperature of the air, the temperature of
  the engine, the barometric pressure, the engine
  load, etc.

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Specification

• In the family of Exhaust Gas Oxygen Sensors,
  there are two types being utilized
• 1. Zirconia Type
• A. Produces a self generating voltage in
  response to exhaust heat and oxygen content.
• 2. Titania Type
• A. Has a variable resistance in response to
  exhaust heat and oxygen content.

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Specification

• This presentation will be focused on the
  Zirconia type of exhaust gas oxygen sensors,
  since the Titania type are known to be a limited
  application
• 1988-90 Jeep (3-wire)
• 1988-92 Chrysler (3-wire)
• 1988-92 Eagle (3-wire)
• 1985-87 Nissan (3-wire)

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Specification

• Exhaust gas oxygen sensors have progressed from
  one wire to the current four and five-wire
  sensors.
• Since the three, four and five-wire sensors have
  heaters, exhaust gas oxygen sensors are being
  placed up and down the exhaust pipe for readings
  which send a signal to the vehicle computer to
  perform certain functions. Hence, you will find
  in some vehicles more than one oxygen sensor.

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Specification

• The Zirconia type of exhaust gas oxygen sensors
  (commonly known as O2 Sensor) is a component of
  an the vehicles emission system.
• This three-way-system component feeds the fuel
  injection ECU information which precisely
  controls the air-fuel mixture ratio of the
  injector system.

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Specification

• The O2 sensor is constantly comparing the amount
  of oxygen inside and outside the engine.
• It is important to remember that should the O2
  sensor become blocked internally (carbon fouled)
  or externally (coated with oil, undercoating,
  antifreeze, or sound coating) this comparison is
  not possible.

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Specification

• The average 87-octane fuel being burned in an
  internal combustion engine is considered to have
  a perfect burn when the air-fuel mixture ratio
  is 14.71.
• (Different fuel mixtures will have different
  perfect ratios.)

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Specification

• Should less air (O2) be in this perfect ratio of
  14.71, then fuel will be left over after
  combustion. This is called a rich mixture. This
  condition creates carbon fouling and can, over
  time, damage spark plugs and catalytic converters
  and the oxygen sensor.
• Should more air (O2) be in this perfect ratio,
  then this is called a lean mixture which tends
  to produce more nitrogen oxide pollutants know as
  NOx. This lean mixture tends to increase
  temperatures in the engine.

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Specification

• The engine computer sends out a bias (constant)
  voltage of 0.45 volts to the fuel system until
  such time that the O2 sensor rises to nominal
  heat range and commences to generate its own
  voltage. This is why the heater was included in
  the oxygen sensor (to bring it up to performance
  temperature quicker).
• When the computer is sending out this bias
  voltage of 0.45 volts (known as an illegal
  value), the system is considered to be in an
  open loop.

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SpecificationsOpen Loop Schematic
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Specification

• Once the O2 sensor comes up to operating
  temperature range (about 600 degrees F) the
  system goes into a closed loop. This is when
  the O2 sensor is in a constant transition between
  high and low voltages (above and below 0.45
  volts), and usually seen as a range between
  plus/minus 0.20 to 0.65 volts. The higher number
  of transitions (known as cross counts) the better
  the O2 sensor is considered to be.
• NTK O2 sensors offer a higher cross count level.

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SpecificationsClosed Loop Schematic
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Specification

• The Zirconia exhaust gas oxygen sensor, being a
  voltage generator, has a potential output of
  between 0 and 1.1 volts DC. The O2 sensor usually
  does not generate its full output until it
  reaches about 600 degrees F. This is why most
  current O2 sensors have a heater making them
  three, four and five-wire O2 sensors. This heater
  assist in enhancing the waiting time for the
  system to commence its full performance. Two of
  the wires are heater wires, one is an isolated
  ground and the other is the sensor signal wire.
  The original one-wire sensor used the shell as a
  ground and corrosion over time created a problem.

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Specification

• The Zirconia exhaust gas oxygen sensor is
  positioned in the exhaust pipe and can detect
  rich and lean mixtures. This involves a
  chemical reaction that generates a voltage. The
  voltage is generated via the properties of ionic
  conductivity of the Zirconia solid electrolyte.
  The engines computer looks at the voltage(s) to
  determine if the mixture is rich or lean, and
  tells the fuel system to adjust the amount of
  fuel entering the engine accordingly.

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Troubleshooting

• Q. How do I know if my exhaust gas oxygen sensor
  is really bad?
• A. Typically general engine performance will be
  noticeably less. Loss of fuel economy will be
  noticed. To be sure, a check of the electronic
  codes should be made. An illuminated engine
  light will also be a good sign (but not
  necessarily show only an O2 sensor problem).

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Testing

• Q. Is it possible to test my O2 sensor while it
  is still attached to my vehicle?
• A. Yes, but certain conditions must be in place
  to make sure your test results are reasonably
  accurate.

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Testing

• Q. How can I test my O2 sensor?
• A. You will need a high impedance volt meter.
• Make sure the engine is at a temperature whereby
  it has gone into a closed loop.
• Make connections to the O2 signal wire and
  observe if you see only 0.45 volts DC. Remember
  you are looking for fluctuations above and below
  0.45 volts, not a constant.
• If you see voltage fluctuations plus/minus 0.20
  to 0.65 volts DC, your O2 sensor is functioning
  properly.

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Testing

• Q. Is it possible to bench test an O2 sensor
  prior to installing?
• A. Yes, but the process is somewhat dangerous and
  is not recommended. The process requires the use
  of a propane flame to bring the sensor up to
  operating temperature. NTK O2 sensors are
  pre-tested prior to being packaged (being evident
  by the discoloration of the end of the O2 sensor
  as if it had been previously installed).

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Warning

• Never attempt to test a Zirconia O2 sensor by
  inserting an outside voltage through the sensor
  signal lead itself. Critical damage can occur to
  the O2 sensor requiring replacement.

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Photos
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