Why They Fail

Oxygen sensors eventually need to be replaced in all vehicles. If your vehicle’s O2 sensor is faulty, chances are there will be signs! Check this list to see if it’s time to replace YOUR vehicle’s oxygen sensors:


      - Sudden decrease in fuel mileage. A defective O2 sensor will likely cause your air-fuel mixture to be too rich and directly affect your fuel economy.

      - Flashing check engine light or malfunction indicator lamp in the vehicle’s dash board. Of course this can happen for other reasons as well (and a defective oxygen sensor is one of them!)

      - Failure to pass smog. According to the EPA (Environmental Protection Agency) and CARB (California Air Resource Board) 50 to 60% of all smog test / emission test related failures are attributed to defective oxygen sensors, causing either low or high CO emissions.

      - Overall poor vehicle performance: rough idling, stalling, hesitation on acceleration, etc.

      - And the most accurate diagnosis is achieved using an OBDII code checker. All cars made in 1996 and after are equipped with an OBDII interface. An OBDII code checker identifies defects in the exhaust system of the car. If your oxygen sensor has failed, the code checker will generate a diagnostic trouble code that specifically indicates your oxygen sensor is bad.



Guidelines for replacing the oxygen sensors in your car:


      - The unheated 1 or 2 wire O2 sensors, used in vehicles from mid-1970s through early 1990s, replace every 40,000 to 50,000 miles.

      - Heated 3 and 4 wire O2 sensors, used in the vehicles from mid-1980s through mid-1990s, replace every 60,000 to 70,000 miles.

      - Newer vehicles made in mid-1990s and later, replace the oxygen sensors every 100,000 miles.


Conclusion, properly functioning oxygen sensors are critical for optimal fuel consumption and good car performance. When in doubt, it is best to replace your faulty oxygen sensor at most, every 100,000 miles.