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Oxygen Sensor Replacement

What is an oxygen sensor?

Most modern engines have two or more oxygen sensors built into the exhaust system, where they provide data for fuel management and emission reduction. Oxygen sensors measure the amount of oxygen in the exhaust gases produced by combustion, and transmit this data to the on board computer. The oxygen sensor closest to the engine and before the catalytic converter, usually termed the upstream sensor, is the more sensitive, and serves to fine tune the air-fuel mixture. The downstream sensor, farthest from the engine and after the catalytic converter, evaluates how well the catalytic converter works.

What are the symptoms of a faulty oxygen sensor?

The engine may not run well, but will still run. Gas mileage will be noticeable poorer, and we may notice a misfire and uneven idling. Since these sensors have an impact on fuel management, particularly the upstream ones, poorly performing sensors will affect other engine components. Oxygen sensors fail with age, heat and weather. Also, coolant and oil leaks into the combustion chamber will shorten the life of sensors as well.

How severe is a faulty oxygen sensor?

A failing oxygen sensor will not leave you stranded on the side of the road, however the repair should not be ignored. An engine that runs poorly will break down faster and lead to higher repair costs, particularly if the catalytic converter fails. Find a good mechanic, one who specializes in fuel management and exhaust work, and set an appointment. Most oxygen sensor can be replaced same day, so plan on losing the car for only a short while.

What is the typical cost to replace a faulty oxygen sensor?

  • Estimated part(s) cost = $80 - $300
  • Estimated labor cost= $35 - $150
  • Estimated total cost = $115 - $450

Repair costs for changing an oxygen sensor will vary depending upon the complexity of the sensor, and the location on the exhaust system. The oxygen sensors before the catalytic converter will cost from $150 to $300, and those after the converter will cost between $80 and $150. There will be a similar division in the installation costs. Sensors before the catalytic converter are, overall, more difficult to access, so labor can cost you $70 to $150. As, for the sensor after the catalytic converter, it is much more accessible, therefore labor costs are lower in the $35 to $60 range.

Keep in mind, pricing will vary by location and your vehicle make and model. If you're not already, save time by using Openbay to compare pricing and book an appointment with a qualified repair shop in your area.

Service article written by an ASE Master Technician