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Oxygen Sensor

 

Oxygen Sensor

An oxygen sensor, as its name implies, senses the concentration of oxygen in the exhaust system. The amount of oxygen remaining in the exhaust gas stream is proportionate to the air and fuel mixture being burned in the cylinders, a critical measure for performance, fuel economy and emissions.

What is an oxygen sensor and how does it work

How Does it Work?

  • Oxygen sensors are galvanic thimbles that act to compare the amount of oxygen in the exhaust with that in the outside or ambient air
  • In a super-heated state, two precious metal electrodes exchange ions through a porous ceramic element
  • This ion flow creates an electrical potential difference that is higher for a rich mixture and lower for a lean mixture
  • Conventional oxygen sensors continually switch between high and low as the mixture adapts and the engine computer (PCM) commands fuel deliver according to the changing oxygen sensor signal

How is it Made?

  • A typical oxygen sensor consists of an extruded steel body, similar to a spark plug, with a special ceramic measuring element sealed into the housing
  • An electrical harness attaches internally to the measuring element and body ground
  • Often contains a special heater assembly to assist the sensor in reaching and maintaining operating temperature

Why Does it Fail?

  • Operates in a harsh environment
  • Contamination
  • Silicates in engine coolant can plug the ceramic lattice structure
  • Oil additives in engine coolant have a similar affect over time

What are the Symptoms of Failure?

  • Poor fuel economy and emissions

What are the Implications of Failure?

  • A vehicle with a failed oxygen sensor will operate normally, but generally will not pass an emissions test
  • Will use an excessive amount of fuel
  • Vehicle may hesitate

How Difficult is the Install?

Difficulty Rating:

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