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Why replace Oxygen Sensors?

Replacing a worn or damaged Oxygen Sensors can:

  • Improve engine efficiency and performance
  • Improve fuel economy (up to 15% savings possible, you could save $100’s a year in fuel costs)
  • Reduce vehicle CO2 and other excessive harmful exhaust emissions
  • Prevent damage to engine or expensive Catalytic Convertors and extend Catalytic Converter life.

Studies from the USA claim oxygen sensor failure is the "single greatest source of excessive emissions for fuel injected vehicles". (Sierra Research Inc. 1996). It is also claimed that In California, 70% of vehicle smog check failures are a result of poorly operating or failed Oxygen Sensors.

The correct function and performance of an oxygen sensor can be affected by many factors which may shorten service life including:

  • Environmental factors such as exposure to carbon, silicone, lead, harmful gases, antifreeze, chemicals, salt, dirt, oil residue or other impurities in the exhaust gases
  • Large temperature fluctuations
  • Poor quality fuel
  • Physical shock or damage

These and many other factors can mean your oxygen sensors require replacement.

During a vehicle service it is recommended to remove the oxygen sensor and visually inspect for signs of these common conditions:

  • Lead poisoning
  • Antifreeze poisoning
  • Silicone poisoning
  • Excessive oil consumption
  • Normal ageing
  • Shock from accidents
  • Excessive oil consumption or leakage

Contamination can come from many sources including:

  • Certain fuel additives
  • Leaded petrol (petrol quality and additives can affect the sensors)
  • Silicone (from incorrect use of silicone gaskets or antifreeze leaking into the cylinders)
  • Phosphorus (from burning oil)
  • Oil, cleaners, water, or other chemicals spilled on the sensor

Some vehicles do have an oxygen sensor "reminder" light to alert the driver when it is time to check the oxygen sensors, MOST DO NOT. In many vehicles the check engine light is illuminated if there is a total failure of the oxygen sensors. However, sensors that are not performing at maximum efficiency may not cause the check engine light to illuminate, and will usually cause the air fuel ratio to move to rich and can cause possible damage to the catalytic converter.

So unless there's a significant driveability problem with the vehicle or a Check Engine light is on, there is no real way of knowing if the oxygen sensor is functioning correctly. See How often to replace oxygen sensors for more information.

Sensor Test Example (Toyota Camry)

In this test example below you can see that the old oxygen sensor (top) is slower than the new sensor (bottom). The old sensor cycles 72 time a minute and the new one 108 cycles a minute.

The only reason this vehicle was tested is because the customer was complaining about vehicle economy, there was no engine warning light.

The only difference from the old to the new is the speed of cycling; note the amplitude is the same on both. This test was carried out at full temperature and at a steady 2500 RPM.

Economy was restored on replacing the O2 Sensor but many technicians would not have picked this as being the problem.

Click to enlarge

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